1 2 Linux Ethernet Bonding Driver HOWTO 3 4 Latest update: 12 November 2007 5 6Initial release : Thomas Davis <tadavis at lbl.gov> 7Corrections, HA extensions : 2000/10/03-15 : 8 - Willy Tarreau <willy at meta-x.org> 9 - Constantine Gavrilov <const-g at xpert.com> 10 - Chad N. Tindel <ctindel at ieee dot org> 11 - Janice Girouard <girouard at us dot ibm dot com> 12 - Jay Vosburgh <fubar at us dot ibm dot com> 13 14Reorganized and updated Feb 2005 by Jay Vosburgh 15Added Sysfs information: 2006/04/24 16 - Mitch Williams <mitch.a.williams at intel.com> 17 18Introduction 19============ 20 21 The Linux bonding driver provides a method for aggregating 22multiple network interfaces into a single logical "bonded" interface. 23The behavior of the bonded interfaces depends upon the mode; generally 24speaking, modes provide either hot standby or load balancing services. 25Additionally, link integrity monitoring may be performed. 26 27 The bonding driver originally came from Donald Becker's 28beowulf patches for kernel 2.0. It has changed quite a bit since, and 29the original tools from extreme-linux and beowulf sites will not work 30with this version of the driver. 31 32 For new versions of the driver, updated userspace tools, and 33who to ask for help, please follow the links at the end of this file. 34 35Table of Contents 36================= 37 381. Bonding Driver Installation 39 402. Bonding Driver Options 41 423. Configuring Bonding Devices 433.1 Configuration with Sysconfig Support 443.1.1 Using DHCP with Sysconfig 453.1.2 Configuring Multiple Bonds with Sysconfig 463.2 Configuration with Initscripts Support 473.2.1 Using DHCP with Initscripts 483.2.2 Configuring Multiple Bonds with Initscripts 493.3 Configuring Bonding Manually with Ifenslave 503.3.1 Configuring Multiple Bonds Manually 513.4 Configuring Bonding Manually via Sysfs 52 534. Querying Bonding Configuration 544.1 Bonding Configuration 554.2 Network Configuration 56 575. Switch Configuration 58 596. 802.1q VLAN Support 60 617. Link Monitoring 627.1 ARP Monitor Operation 637.2 Configuring Multiple ARP Targets 647.3 MII Monitor Operation 65 668. Potential Trouble Sources 678.1 Adventures in Routing 688.2 Ethernet Device Renaming 698.3 Painfully Slow Or No Failed Link Detection By Miimon 70 719. SNMP agents 72 7310. Promiscuous mode 74 7511. Configuring Bonding for High Availability 7611.1 High Availability in a Single Switch Topology 7711.2 High Availability in a Multiple Switch Topology 7811.2.1 HA Bonding Mode Selection for Multiple Switch Topology 7911.2.2 HA Link Monitoring for Multiple Switch Topology 80 8112. Configuring Bonding for Maximum Throughput 8212.1 Maximum Throughput in a Single Switch Topology 8312.1.1 MT Bonding Mode Selection for Single Switch Topology 8412.1.2 MT Link Monitoring for Single Switch Topology 8512.2 Maximum Throughput in a Multiple Switch Topology 8612.2.1 MT Bonding Mode Selection for Multiple Switch Topology 8712.2.2 MT Link Monitoring for Multiple Switch Topology 88 8913. Switch Behavior Issues 9013.1 Link Establishment and Failover Delays 9113.2 Duplicated Incoming Packets 92 9314. Hardware Specific Considerations 9414.1 IBM BladeCenter 95 9615. Frequently Asked Questions 97 9816. Resources and Links 99 100 1011. Bonding Driver Installation 102============================== 103 104 Most popular distro kernels ship with the bonding driver 105already available as a module and the ifenslave user level control 106program installed and ready for use. If your distro does not, or you 107have need to compile bonding from source (e.g., configuring and 108installing a mainline kernel from kernel.org), you'll need to perform 109the following steps: 110 1111.1 Configure and build the kernel with bonding 112----------------------------------------------- 113 114 The current version of the bonding driver is available in the 115drivers/net/bonding subdirectory of the most recent kernel source 116(which is available on http://kernel.org). Most users "rolling their 117own" will want to use the most recent kernel from kernel.org. 118 119 Configure kernel with "make menuconfig" (or "make xconfig" or 120"make config"), then select "Bonding driver support" in the "Network 121device support" section. It is recommended that you configure the 122driver as module since it is currently the only way to pass parameters 123to the driver or configure more than one bonding device. 124 125 Build and install the new kernel and modules, then continue 126below to install ifenslave. 127 1281.2 Install ifenslave Control Utility 129------------------------------------- 130 131 The ifenslave user level control program is included in the 132kernel source tree, in the file Documentation/networking/ifenslave.c. 133It is generally recommended that you use the ifenslave that 134corresponds to the kernel that you are using (either from the same 135source tree or supplied with the distro), however, ifenslave 136executables from older kernels should function (but features newer 137than the ifenslave release are not supported). Running an ifenslave 138that is newer than the kernel is not supported, and may or may not 139work. 140 141 To install ifenslave, do the following: 142 143# gcc -Wall -O -I/usr/src/linux/include ifenslave.c -o ifenslave 144# cp ifenslave /sbin/ifenslave 145 146 If your kernel source is not in "/usr/src/linux," then replace 147"/usr/src/linux/include" in the above with the location of your kernel 148source include directory. 149 150 You may wish to back up any existing /sbin/ifenslave, or, for 151testing or informal use, tag the ifenslave to the kernel version 152(e.g., name the ifenslave executable /sbin/ifenslave-2.6.10). 153 154IMPORTANT NOTE: 155 156 If you omit the "-I" or specify an incorrect directory, you 157may end up with an ifenslave that is incompatible with the kernel 158you're trying to build it for. Some distros (e.g., Red Hat from 7.1 159onwards) do not have /usr/include/linux symbolically linked to the 160default kernel source include directory. 161 162SECOND IMPORTANT NOTE: 163 If you plan to configure bonding using sysfs, you do not need 164to use ifenslave. 165 1662. Bonding Driver Options 167========================= 168 169 Options for the bonding driver are supplied as parameters to the 170bonding module at load time, or are specified via sysfs. 171 172 Module options may be given as command line arguments to the 173insmod or modprobe command, but are usually specified in either the 174/etc/modules.conf or /etc/modprobe.conf configuration file, or in a 175distro-specific configuration file (some of which are detailed in the next 176section). 177 178 Details on bonding support for sysfs is provided in the 179"Configuring Bonding Manually via Sysfs" section, below. 180 181 The available bonding driver parameters are listed below. If a 182parameter is not specified the default value is used. When initially 183configuring a bond, it is recommended "tail -f /var/log/messages" be 184run in a separate window to watch for bonding driver error messages. 185 186 It is critical that either the miimon or arp_interval and 187arp_ip_target parameters be specified, otherwise serious network 188degradation will occur during link failures. Very few devices do not 189support at least miimon, so there is really no reason not to use it. 190 191 Options with textual values will accept either the text name 192or, for backwards compatibility, the option value. E.g., 193"mode=802.3ad" and "mode=4" set the same mode. 194 195 The parameters are as follows: 196 197ad_select 198 199 Specifies the 802.3ad aggregation selection logic to use. The 200 possible values and their effects are: 201 202 stable or 0 203 204 The active aggregator is chosen by largest aggregate 205 bandwidth. 206 207 Reselection of the active aggregator occurs only when all 208 slaves of the active aggregator are down or the active 209 aggregator has no slaves. 210 211 This is the default value. 212 213 bandwidth or 1 214 215 The active aggregator is chosen by largest aggregate 216 bandwidth. Reselection occurs if: 217 218 - A slave is added to or removed from the bond 219 220 - Any slave's link state changes 221 222 - Any slave's 802.3ad association state changes 223 224 - The bond's adminstrative state changes to up 225 226 count or 2 227 228 The active aggregator is chosen by the largest number of 229 ports (slaves). Reselection occurs as described under the 230 "bandwidth" setting, above. 231 232 The bandwidth and count selection policies permit failover of 233 802.3ad aggregations when partial failure of the active aggregator 234 occurs. This keeps the aggregator with the highest availability 235 (either in bandwidth or in number of ports) active at all times. 236 237 This option was added in bonding version 3.4.0. 238 239arp_interval 240 241 Specifies the ARP link monitoring frequency in milliseconds. 242 243 The ARP monitor works by periodically checking the slave 244 devices to determine whether they have sent or received 245 traffic recently (the precise criteria depends upon the 246 bonding mode, and the state of the slave). Regular traffic is 247 generated via ARP probes issued for the addresses specified by 248 the arp_ip_target option. 249 250 This behavior can be modified by the arp_validate option, 251 below. 252 253 If ARP monitoring is used in an etherchannel compatible mode 254 (modes 0 and 2), the switch should be configured in a mode 255 that evenly distributes packets across all links. If the 256 switch is configured to distribute the packets in an XOR 257 fashion, all replies from the ARP targets will be received on 258 the same link which could cause the other team members to 259 fail. ARP monitoring should not be used in conjunction with 260 miimon. A value of 0 disables ARP monitoring. The default 261 value is 0. 262 263arp_ip_target 264 265 Specifies the IP addresses to use as ARP monitoring peers when 266 arp_interval is > 0. These are the targets of the ARP request 267 sent to determine the health of the link to the targets. 268 Specify these values in ddd.ddd.ddd.ddd format. Multiple IP 269 addresses must be separated by a comma. At least one IP 270 address must be given for ARP monitoring to function. The 271 maximum number of targets that can be specified is 16. The 272 default value is no IP addresses. 273 274arp_validate 275 276 Specifies whether or not ARP probes and replies should be 277 validated in the active-backup mode. This causes the ARP 278 monitor to examine the incoming ARP requests and replies, and 279 only consider a slave to be up if it is receiving the 280 appropriate ARP traffic. 281 282 Possible values are: 283 284 none or 0 285 286 No validation is performed. This is the default. 287 288 active or 1 289 290 Validation is performed only for the active slave. 291 292 backup or 2 293 294 Validation is performed only for backup slaves. 295 296 all or 3 297 298 Validation is performed for all slaves. 299 300 For the active slave, the validation checks ARP replies to 301 confirm that they were generated by an arp_ip_target. Since 302 backup slaves do not typically receive these replies, the 303 validation performed for backup slaves is on the ARP request 304 sent out via the active slave. It is possible that some 305 switch or network configurations may result in situations 306 wherein the backup slaves do not receive the ARP requests; in 307 such a situation, validation of backup slaves must be 308 disabled. 309 310 This option is useful in network configurations in which 311 multiple bonding hosts are concurrently issuing ARPs to one or 312 more targets beyond a common switch. Should the link between 313 the switch and target fail (but not the switch itself), the 314 probe traffic generated by the multiple bonding instances will 315 fool the standard ARP monitor into considering the links as 316 still up. Use of the arp_validate option can resolve this, as 317 the ARP monitor will only consider ARP requests and replies 318 associated with its own instance of bonding. 319 320 This option was added in bonding version 3.1.0. 321 322downdelay 323 324 Specifies the time, in milliseconds, to wait before disabling 325 a slave after a link failure has been detected. This option 326 is only valid for the miimon link monitor. The downdelay 327 value should be a multiple of the miimon value; if not, it 328 will be rounded down to the nearest multiple. The default 329 value is 0. 330 331fail_over_mac 332 333 Specifies whether active-backup mode should set all slaves to 334 the same MAC address at enslavement (the traditional 335 behavior), or, when enabled, perform special handling of the 336 bond's MAC address in accordance with the selected policy. 337 338 Possible values are: 339 340 none or 0 341 342 This setting disables fail_over_mac, and causes 343 bonding to set all slaves of an active-backup bond to 344 the same MAC address at enslavement time. This is the 345 default. 346 347 active or 1 348 349 The "active" fail_over_mac policy indicates that the 350 MAC address of the bond should always be the MAC 351 address of the currently active slave. The MAC 352 address of the slaves is not changed; instead, the MAC 353 address of the bond changes during a failover. 354 355 This policy is useful for devices that cannot ever 356 alter their MAC address, or for devices that refuse 357 incoming broadcasts with their own source MAC (which 358 interferes with the ARP monitor). 359 360 The down side of this policy is that every device on 361 the network must be updated via gratuitous ARP, 362 vs. just updating a switch or set of switches (which 363 often takes place for any traffic, not just ARP 364 traffic, if the switch snoops incoming traffic to 365 update its tables) for the traditional method. If the 366 gratuitous ARP is lost, communication may be 367 disrupted. 368 369 When this policy is used in conjuction with the mii 370 monitor, devices which assert link up prior to being 371 able to actually transmit and receive are particularly 372 susecptible to loss of the gratuitous ARP, and an 373 appropriate updelay setting may be required. 374 375 follow or 2 376 377 The "follow" fail_over_mac policy causes the MAC 378 address of the bond to be selected normally (normally 379 the MAC address of the first slave added to the bond). 380 However, the second and subsequent slaves are not set 381 to this MAC address while they are in a backup role; a 382 slave is programmed with the bond's MAC address at 383 failover time (and the formerly active slave receives 384 the newly active slave's MAC address). 385 386 This policy is useful for multiport devices that 387 either become confused or incur a performance penalty 388 when multiple ports are programmed with the same MAC 389 address. 390 391 392 The default policy is none, unless the first slave cannot 393 change its MAC address, in which case the active policy is 394 selected by default. 395 396 This option may be modified via sysfs only when no slaves are 397 present in the bond. 398 399 This option was added in bonding version 3.2.0. The "follow" 400 policy was added in bonding version 3.3.0. 401 402lacp_rate 403 404 Option specifying the rate in which we'll ask our link partner 405 to transmit LACPDU packets in 802.3ad mode. Possible values 406 are: 407 408 slow or 0 409 Request partner to transmit LACPDUs every 30 seconds 410 411 fast or 1 412 Request partner to transmit LACPDUs every 1 second 413 414 The default is slow. 415 416max_bonds 417 418 Specifies the number of bonding devices to create for this 419 instance of the bonding driver. E.g., if max_bonds is 3, and 420 the bonding driver is not already loaded, then bond0, bond1 421 and bond2 will be created. The default value is 1. Specifying 422 a value of 0 will load bonding, but will not create any devices. 423 424miimon 425 426 Specifies the MII link monitoring frequency in milliseconds. 427 This determines how often the link state of each slave is 428 inspected for link failures. A value of zero disables MII 429 link monitoring. A value of 100 is a good starting point. 430 The use_carrier option, below, affects how the link state is 431 determined. See the High Availability section for additional 432 information. The default value is 0. 433 434mode 435 436 Specifies one of the bonding policies. The default is 437 balance-rr (round robin). Possible values are: 438 439 balance-rr or 0 440 441 Round-robin policy: Transmit packets in sequential 442 order from the first available slave through the 443 last. This mode provides load balancing and fault 444 tolerance. 445 446 active-backup or 1 447 448 Active-backup policy: Only one slave in the bond is 449 active. A different slave becomes active if, and only 450 if, the active slave fails. The bond's MAC address is 451 externally visible on only one port (network adapter) 452 to avoid confusing the switch. 453 454 In bonding version 2.6.2 or later, when a failover 455 occurs in active-backup mode, bonding will issue one 456 or more gratuitous ARPs on the newly active slave. 457 One gratuitous ARP is issued for the bonding master 458 interface and each VLAN interfaces configured above 459 it, provided that the interface has at least one IP 460 address configured. Gratuitous ARPs issued for VLAN 461 interfaces are tagged with the appropriate VLAN id. 462 463 This mode provides fault tolerance. The primary 464 option, documented below, affects the behavior of this 465 mode. 466 467 balance-xor or 2 468 469 XOR policy: Transmit based on the selected transmit 470 hash policy. The default policy is a simple [(source 471 MAC address XOR'd with destination MAC address) modulo 472 slave count]. Alternate transmit policies may be 473 selected via the xmit_hash_policy option, described 474 below. 475 476 This mode provides load balancing and fault tolerance. 477 478 broadcast or 3 479 480 Broadcast policy: transmits everything on all slave 481 interfaces. This mode provides fault tolerance. 482 483 802.3ad or 4 484 485 IEEE 802.3ad Dynamic link aggregation. Creates 486 aggregation groups that share the same speed and 487 duplex settings. Utilizes all slaves in the active 488 aggregator according to the 802.3ad specification. 489 490 Slave selection for outgoing traffic is done according 491 to the transmit hash policy, which may be changed from 492 the default simple XOR policy via the xmit_hash_policy 493 option, documented below. Note that not all transmit 494 policies may be 802.3ad compliant, particularly in 495 regards to the packet mis-ordering requirements of 496 section 43.2.4 of the 802.3ad standard. Differing 497 peer implementations will have varying tolerances for 498 noncompliance. 499 500 Prerequisites: 501 502 1. Ethtool support in the base drivers for retrieving 503 the speed and duplex of each slave. 504 505 2. A switch that supports IEEE 802.3ad Dynamic link 506 aggregation. 507 508 Most switches will require some type of configuration 509 to enable 802.3ad mode. 510 511 balance-tlb or 5 512 513 Adaptive transmit load balancing: channel bonding that 514 does not require any special switch support. The 515 outgoing traffic is distributed according to the 516 current load (computed relative to the speed) on each 517 slave. Incoming traffic is received by the current 518 slave. If the receiving slave fails, another slave 519 takes over the MAC address of the failed receiving 520 slave. 521 522 Prerequisite: 523 524 Ethtool support in the base drivers for retrieving the 525 speed of each slave. 526 527 balance-alb or 6 528 529 Adaptive load balancing: includes balance-tlb plus 530 receive load balancing (rlb) for IPV4 traffic, and 531 does not require any special switch support. The 532 receive load balancing is achieved by ARP negotiation. 533 The bonding driver intercepts the ARP Replies sent by 534 the local system on their way out and overwrites the 535 source hardware address with the unique hardware 536 address of one of the slaves in the bond such that 537 different peers use different hardware addresses for 538 the server. 539 540 Receive traffic from connections created by the server 541 is also balanced. When the local system sends an ARP 542 Request the bonding driver copies and saves the peer's 543 IP information from the ARP packet. When the ARP 544 Reply arrives from the peer, its hardware address is 545 retrieved and the bonding driver initiates an ARP 546 reply to this peer assigning it to one of the slaves 547 in the bond. A problematic outcome of using ARP 548 negotiation for balancing is that each time that an 549 ARP request is broadcast it uses the hardware address 550 of the bond. Hence, peers learn the hardware address 551 of the bond and the balancing of receive traffic 552 collapses to the current slave. This is handled by 553 sending updates (ARP Replies) to all the peers with 554 their individually assigned hardware address such that 555 the traffic is redistributed. Receive traffic is also 556 redistributed when a new slave is added to the bond 557 and when an inactive slave is re-activated. The 558 receive load is distributed sequentially (round robin) 559 among the group of highest speed slaves in the bond. 560 561 When a link is reconnected or a new slave joins the 562 bond the receive traffic is redistributed among all 563 active slaves in the bond by initiating ARP Replies 564 with the selected MAC address to each of the 565 clients. The updelay parameter (detailed below) must 566 be set to a value equal or greater than the switch's 567 forwarding delay so that the ARP Replies sent to the 568 peers will not be blocked by the switch. 569 570 Prerequisites: 571 572 1. Ethtool support in the base drivers for retrieving 573 the speed of each slave. 574 575 2. Base driver support for setting the hardware 576 address of a device while it is open. This is 577 required so that there will always be one slave in the 578 team using the bond hardware address (the 579 curr_active_slave) while having a unique hardware 580 address for each slave in the bond. If the 581 curr_active_slave fails its hardware address is 582 swapped with the new curr_active_slave that was 583 chosen. 584 585num_grat_arp 586 587 Specifies the number of gratuitous ARPs to be issued after a 588 failover event. One gratuitous ARP is issued immediately after 589 the failover, subsequent ARPs are sent at a rate of one per link 590 monitor interval (arp_interval or miimon, whichever is active). 591 592 The valid range is 0 - 255; the default value is 1. This option 593 affects only the active-backup mode. This option was added for 594 bonding version 3.3.0. 595 596num_unsol_na 597 598 Specifies the number of unsolicited IPv6 Neighbor Advertisements 599 to be issued after a failover event. One unsolicited NA is issued 600 immediately after the failover. 601 602 The valid range is 0 - 255; the default value is 1. This option 603 affects only the active-backup mode. This option was added for 604 bonding version 3.4.0. 605 606primary 607 608 A string (eth0, eth2, etc) specifying which slave is the 609 primary device. The specified device will always be the 610 active slave while it is available. Only when the primary is 611 off-line will alternate devices be used. This is useful when 612 one slave is preferred over another, e.g., when one slave has 613 higher throughput than another. 614 615 The primary option is only valid for active-backup mode. 616 617updelay 618 619 Specifies the time, in milliseconds, to wait before enabling a 620 slave after a link recovery has been detected. This option is 621 only valid for the miimon link monitor. The updelay value 622 should be a multiple of the miimon value; if not, it will be 623 rounded down to the nearest multiple. The default value is 0. 624 625use_carrier 626 627 Specifies whether or not miimon should use MII or ETHTOOL 628 ioctls vs. netif_carrier_ok() to determine the link 629 status. The MII or ETHTOOL ioctls are less efficient and 630 utilize a deprecated calling sequence within the kernel. The 631 netif_carrier_ok() relies on the device driver to maintain its 632 state with netif_carrier_on/off; at this writing, most, but 633 not all, device drivers support this facility. 634 635 If bonding insists that the link is up when it should not be, 636 it may be that your network device driver does not support 637 netif_carrier_on/off. The default state for netif_carrier is 638 "carrier on," so if a driver does not support netif_carrier, 639 it will appear as if the link is always up. In this case, 640 setting use_carrier to 0 will cause bonding to revert to the 641 MII / ETHTOOL ioctl method to determine the link state. 642 643 A value of 1 enables the use of netif_carrier_ok(), a value of 644 0 will use the deprecated MII / ETHTOOL ioctls. The default 645 value is 1. 646 647xmit_hash_policy 648 649 Selects the transmit hash policy to use for slave selection in 650 balance-xor and 802.3ad modes. Possible values are: 651 652 layer2 653 654 Uses XOR of hardware MAC addresses to generate the 655 hash. The formula is 656 657 (source MAC XOR destination MAC) modulo slave count 658 659 This algorithm will place all traffic to a particular 660 network peer on the same slave. 661 662 This algorithm is 802.3ad compliant. 663 664 layer2+3 665 666 This policy uses a combination of layer2 and layer3 667 protocol information to generate the hash. 668 669 Uses XOR of hardware MAC addresses and IP addresses to 670 generate the hash. The formula is 671 672 (((source IP XOR dest IP) AND 0xffff) XOR 673 ( source MAC XOR destination MAC )) 674 modulo slave count 675 676 This algorithm will place all traffic to a particular 677 network peer on the same slave. For non-IP traffic, 678 the formula is the same as for the layer2 transmit 679 hash policy. 680 681 This policy is intended to provide a more balanced 682 distribution of traffic than layer2 alone, especially 683 in environments where a layer3 gateway device is 684 required to reach most destinations. 685 686 This algorithm is 802.3ad compliant. 687 688 layer3+4 689 690 This policy uses upper layer protocol information, 691 when available, to generate the hash. This allows for 692 traffic to a particular network peer to span multiple 693 slaves, although a single connection will not span 694 multiple slaves. 695 696 The formula for unfragmented TCP and UDP packets is 697 698 ((source port XOR dest port) XOR 699 ((source IP XOR dest IP) AND 0xffff) 700 modulo slave count 701 702 For fragmented TCP or UDP packets and all other IP 703 protocol traffic, the source and destination port 704 information is omitted. For non-IP traffic, the 705 formula is the same as for the layer2 transmit hash 706 policy. 707 708 This policy is intended to mimic the behavior of 709 certain switches, notably Cisco switches with PFC2 as 710 well as some Foundry and IBM products. 711 712 This algorithm is not fully 802.3ad compliant. A 713 single TCP or UDP conversation containing both 714 fragmented and unfragmented packets will see packets 715 striped across two interfaces. This may result in out 716 of order delivery. Most traffic types will not meet 717 this criteria, as TCP rarely fragments traffic, and 718 most UDP traffic is not involved in extended 719 conversations. Other implementations of 802.3ad may 720 or may not tolerate this noncompliance. 721 722 The default value is layer2. This option was added in bonding 723 version 2.6.3. In earlier versions of bonding, this parameter 724 does not exist, and the layer2 policy is the only policy. The 725 layer2+3 value was added for bonding version 3.2.2. 726 727 7283. Configuring Bonding Devices 729============================== 730 731 You can configure bonding using either your distro's network 732initialization scripts, or manually using either ifenslave or the 733sysfs interface. Distros generally use one of two packages for the 734network initialization scripts: initscripts or sysconfig. Recent 735versions of these packages have support for bonding, while older 736versions do not. 737 738 We will first describe the options for configuring bonding for 739distros using versions of initscripts and sysconfig with full or 740partial support for bonding, then provide information on enabling 741bonding without support from the network initialization scripts (i.e., 742older versions of initscripts or sysconfig). 743 744 If you're unsure whether your distro uses sysconfig or 745initscripts, or don't know if it's new enough, have no fear. 746Determining this is fairly straightforward. 747 748 First, issue the command: 749 750$ rpm -qf /sbin/ifup 751 752 It will respond with a line of text starting with either 753"initscripts" or "sysconfig," followed by some numbers. This is the 754package that provides your network initialization scripts. 755 756 Next, to determine if your installation supports bonding, 757issue the command: 758 759$ grep ifenslave /sbin/ifup 760 761 If this returns any matches, then your initscripts or 762sysconfig has support for bonding. 763 7643.1 Configuration with Sysconfig Support 765---------------------------------------- 766 767 This section applies to distros using a version of sysconfig 768with bonding support, for example, SuSE Linux Enterprise Server 9. 769 770 SuSE SLES 9's networking configuration system does support 771bonding, however, at this writing, the YaST system configuration 772front end does not provide any means to work with bonding devices. 773Bonding devices can be managed by hand, however, as follows. 774 775 First, if they have not already been configured, configure the 776slave devices. On SLES 9, this is most easily done by running the 777yast2 sysconfig configuration utility. The goal is for to create an 778ifcfg-id file for each slave device. The simplest way to accomplish 779this is to configure the devices for DHCP (this is only to get the 780file ifcfg-id file created; see below for some issues with DHCP). The 781name of the configuration file for each device will be of the form: 782 783ifcfg-id-xx:xx:xx:xx:xx:xx 784 785 Where the "xx" portion will be replaced with the digits from 786the device's permanent MAC address. 787 788 Once the set of ifcfg-id-xx:xx:xx:xx:xx:xx files has been 789created, it is necessary to edit the configuration files for the slave 790devices (the MAC addresses correspond to those of the slave devices). 791Before editing, the file will contain multiple lines, and will look 792something like this: 793 794BOOTPROTO='dhcp' 795STARTMODE='on' 796USERCTL='no' 797UNIQUE='XNzu.WeZGOGF+4wE' 798_nm_name='bus-pci-0001:61:01.0' 799 800 Change the BOOTPROTO and STARTMODE lines to the following: 801 802BOOTPROTO='none' 803STARTMODE='off' 804 805 Do not alter the UNIQUE or _nm_name lines. Remove any other 806lines (USERCTL, etc). 807 808 Once the ifcfg-id-xx:xx:xx:xx:xx:xx files have been modified, 809it's time to create the configuration file for the bonding device 810itself. This file is named ifcfg-bondX, where X is the number of the 811bonding device to create, starting at 0. The first such file is 812ifcfg-bond0, the second is ifcfg-bond1, and so on. The sysconfig 813network configuration system will correctly start multiple instances 814of bonding. 815 816 The contents of the ifcfg-bondX file is as follows: 817 818BOOTPROTO="static" 819BROADCAST="10.0.2.255" 820IPADDR="10.0.2.10" 821NETMASK="255.255.0.0" 822NETWORK="10.0.2.0" 823REMOTE_IPADDR="" 824STARTMODE="onboot" 825BONDING_MASTER="yes" 826BONDING_MODULE_OPTS="mode=active-backup miimon=100" 827BONDING_SLAVE0="eth0" 828BONDING_SLAVE1="bus-pci-0000:06:08.1" 829 830 Replace the sample BROADCAST, IPADDR, NETMASK and NETWORK 831values with the appropriate values for your network. 832 833 The STARTMODE specifies when the device is brought online. 834The possible values are: 835 836 onboot: The device is started at boot time. If you're not 837 sure, this is probably what you want. 838 839 manual: The device is started only when ifup is called 840 manually. Bonding devices may be configured this 841 way if you do not wish them to start automatically 842 at boot for some reason. 843 844 hotplug: The device is started by a hotplug event. This is not 845 a valid choice for a bonding device. 846 847 off or ignore: The device configuration is ignored. 848 849 The line BONDING_MASTER='yes' indicates that the device is a 850bonding master device. The only useful value is "yes." 851 852 The contents of BONDING_MODULE_OPTS are supplied to the 853instance of the bonding module for this device. Specify the options 854for the bonding mode, link monitoring, and so on here. Do not include 855the max_bonds bonding parameter; this will confuse the configuration 856system if you have multiple bonding devices. 857 858 Finally, supply one BONDING_SLAVEn="slave device" for each 859slave. where "n" is an increasing value, one for each slave. The 860"slave device" is either an interface name, e.g., "eth0", or a device 861specifier for the network device. The interface name is easier to 862find, but the ethN names are subject to change at boot time if, e.g., 863a device early in the sequence has failed. The device specifiers 864(bus-pci-0000:06:08.1 in the example above) specify the physical 865network device, and will not change unless the device's bus location 866changes (for example, it is moved from one PCI slot to another). The 867example above uses one of each type for demonstration purposes; most 868configurations will choose one or the other for all slave devices. 869 870 When all configuration files have been modified or created, 871networking must be restarted for the configuration changes to take 872effect. This can be accomplished via the following: 873 874# /etc/init.d/network restart 875 876 Note that the network control script (/sbin/ifdown) will 877remove the bonding module as part of the network shutdown processing, 878so it is not necessary to remove the module by hand if, e.g., the 879module parameters have changed. 880 881 Also, at this writing, YaST/YaST2 will not manage bonding 882devices (they do not show bonding interfaces on its list of network 883devices). It is necessary to edit the configuration file by hand to 884change the bonding configuration. 885 886 Additional general options and details of the ifcfg file 887format can be found in an example ifcfg template file: 888 889/etc/sysconfig/network/ifcfg.template 890 891 Note that the template does not document the various BONDING_ 892settings described above, but does describe many of the other options. 893 8943.1.1 Using DHCP with Sysconfig 895------------------------------- 896 897 Under sysconfig, configuring a device with BOOTPROTO='dhcp' 898will cause it to query DHCP for its IP address information. At this 899writing, this does not function for bonding devices; the scripts 900attempt to obtain the device address from DHCP prior to adding any of 901the slave devices. Without active slaves, the DHCP requests are not 902sent to the network. 903 9043.1.2 Configuring Multiple Bonds with Sysconfig 905----------------------------------------------- 906 907 The sysconfig network initialization system is capable of 908handling multiple bonding devices. All that is necessary is for each 909bonding instance to have an appropriately configured ifcfg-bondX file 910(as described above). Do not specify the "max_bonds" parameter to any 911instance of bonding, as this will confuse sysconfig. If you require 912multiple bonding devices with identical parameters, create multiple 913ifcfg-bondX files. 914 915 Because the sysconfig scripts supply the bonding module 916options in the ifcfg-bondX file, it is not necessary to add them to 917the system /etc/modules.conf or /etc/modprobe.conf configuration file. 918 9193.2 Configuration with Initscripts Support 920------------------------------------------ 921 922 This section applies to distros using a recent version of 923initscripts with bonding support, for example, Red Hat Enterprise Linux 924version 3 or later, Fedora, etc. On these systems, the network 925initialization scripts have knowledge of bonding, and can be configured to 926control bonding devices. Note that older versions of the initscripts 927package have lower levels of support for bonding; this will be noted where 928applicable. 929 930 These distros will not automatically load the network adapter 931driver unless the ethX device is configured with an IP address. 932Because of this constraint, users must manually configure a 933network-script file for all physical adapters that will be members of 934a bondX link. Network script files are located in the directory: 935 936/etc/sysconfig/network-scripts 937 938 The file name must be prefixed with "ifcfg-eth" and suffixed 939with the adapter's physical adapter number. For example, the script 940for eth0 would be named /etc/sysconfig/network-scripts/ifcfg-eth0. 941Place the following text in the file: 942 943DEVICE=eth0 944USERCTL=no 945ONBOOT=yes 946MASTER=bond0 947SLAVE=yes 948BOOTPROTO=none 949 950 The DEVICE= line will be different for every ethX device and 951must correspond with the name of the file, i.e., ifcfg-eth1 must have 952a device line of DEVICE=eth1. The setting of the MASTER= line will 953also depend on the final bonding interface name chosen for your bond. 954As with other network devices, these typically start at 0, and go up 955one for each device, i.e., the first bonding instance is bond0, the 956second is bond1, and so on. 957 958 Next, create a bond network script. The file name for this 959script will be /etc/sysconfig/network-scripts/ifcfg-bondX where X is 960the number of the bond. For bond0 the file is named "ifcfg-bond0", 961for bond1 it is named "ifcfg-bond1", and so on. Within that file, 962place the following text: 963 964DEVICE=bond0 965IPADDR=192.168.1.1 966NETMASK=255.255.255.0 967NETWORK=192.168.1.0 968BROADCAST=192.168.1.255 969ONBOOT=yes 970BOOTPROTO=none 971USERCTL=no 972 973 Be sure to change the networking specific lines (IPADDR, 974NETMASK, NETWORK and BROADCAST) to match your network configuration. 975 976 For later versions of initscripts, such as that found with Fedora 9777 (or later) and Red Hat Enterprise Linux version 5 (or later), it is possible, 978and, indeed, preferable, to specify the bonding options in the ifcfg-bond0 979file, e.g. a line of the format: 980 981BONDING_OPTS="mode=active-backup arp_interval=60 arp_ip_target=192.168.1.254" 982 983 will configure the bond with the specified options. The options 984specified in BONDING_OPTS are identical to the bonding module parameters 985except for the arp_ip_target field when using versions of initscripts older 986than and 8.57 (Fedora 8) and 8.45.19 (Red Hat Enterprise Linux 5.2). When 987using older versions each target should be included as a separate option and 988should be preceded by a '+' to indicate it should be added to the list of 989queried targets, e.g., 990 991 arp_ip_target=+192.168.1.1 arp_ip_target=+192.168.1.2 992 993 is the proper syntax to specify multiple targets. When specifying 994options via BONDING_OPTS, it is not necessary to edit /etc/modules.conf or 995/etc/modprobe.conf. 996 997 For even older versions of initscripts that do not support 998BONDING_OPTS, it is necessary to edit /etc/modules.conf (or 999/etc/modprobe.conf, depending upon your distro) to load the bonding module 1000with your desired options when the bond0 interface is brought up. The 1001following lines in /etc/modules.conf (or modprobe.conf) will load the 1002bonding module, and select its options: 1003 1004alias bond0 bonding 1005options bond0 mode=balance-alb miimon=100 1006 1007 Replace the sample parameters with the appropriate set of 1008options for your configuration. 1009 1010 Finally run "/etc/rc.d/init.d/network restart" as root. This 1011will restart the networking subsystem and your bond link should be now 1012up and running. 1013 10143.2.1 Using DHCP with Initscripts 1015--------------------------------- 1016 1017 Recent versions of initscripts (the versions supplied with Fedora 1018Core 3 and Red Hat Enterprise Linux 4, or later versions, are reported to 1019work) have support for assigning IP information to bonding devices via 1020DHCP. 1021 1022 To configure bonding for DHCP, configure it as described 1023above, except replace the line "BOOTPROTO=none" with "BOOTPROTO=dhcp" 1024and add a line consisting of "TYPE=Bonding". Note that the TYPE value 1025is case sensitive. 1026 10273.2.2 Configuring Multiple Bonds with Initscripts 1028------------------------------------------------- 1029 1030 Initscripts packages that are included with Fedora 7 and Red Hat 1031Enterprise Linux 5 support multiple bonding interfaces by simply 1032specifying the appropriate BONDING_OPTS= in ifcfg-bondX where X is the 1033number of the bond. This support requires sysfs support in the kernel, 1034and a bonding driver of version 3.0.0 or later. Other configurations may 1035not support this method for specifying multiple bonding interfaces; for 1036those instances, see the "Configuring Multiple Bonds Manually" section, 1037below. 1038 10393.3 Configuring Bonding Manually with Ifenslave 1040----------------------------------------------- 1041 1042 This section applies to distros whose network initialization 1043scripts (the sysconfig or initscripts package) do not have specific 1044knowledge of bonding. One such distro is SuSE Linux Enterprise Server 1045version 8. 1046 1047 The general method for these systems is to place the bonding 1048module parameters into /etc/modules.conf or /etc/modprobe.conf (as 1049appropriate for the installed distro), then add modprobe and/or 1050ifenslave commands to the system's global init script. The name of 1051the global init script differs; for sysconfig, it is 1052/etc/init.d/boot.local and for initscripts it is /etc/rc.d/rc.local. 1053 1054 For example, if you wanted to make a simple bond of two e100 1055devices (presumed to be eth0 and eth1), and have it persist across 1056reboots, edit the appropriate file (/etc/init.d/boot.local or 1057/etc/rc.d/rc.local), and add the following: 1058 1059modprobe bonding mode=balance-alb miimon=100 1060modprobe e100 1061ifconfig bond0 192.168.1.1 netmask 255.255.255.0 up 1062ifenslave bond0 eth0 1063ifenslave bond0 eth1 1064 1065 Replace the example bonding module parameters and bond0 1066network configuration (IP address, netmask, etc) with the appropriate 1067values for your configuration. 1068 1069 Unfortunately, this method will not provide support for the 1070ifup and ifdown scripts on the bond devices. To reload the bonding 1071configuration, it is necessary to run the initialization script, e.g., 1072 1073# /etc/init.d/boot.local 1074 1075 or 1076 1077# /etc/rc.d/rc.local 1078 1079 It may be desirable in such a case to create a separate script 1080which only initializes the bonding configuration, then call that 1081separate script from within boot.local. This allows for bonding to be 1082enabled without re-running the entire global init script. 1083 1084 To shut down the bonding devices, it is necessary to first 1085mark the bonding device itself as being down, then remove the 1086appropriate device driver modules. For our example above, you can do 1087the following: 1088 1089# ifconfig bond0 down 1090# rmmod bonding 1091# rmmod e100 1092 1093 Again, for convenience, it may be desirable to create a script 1094with these commands. 1095 1096 10973.3.1 Configuring Multiple Bonds Manually 1098----------------------------------------- 1099 1100 This section contains information on configuring multiple 1101bonding devices with differing options for those systems whose network 1102initialization scripts lack support for configuring multiple bonds. 1103 1104 If you require multiple bonding devices, but all with the same 1105options, you may wish to use the "max_bonds" module parameter, 1106documented above. 1107 1108 To create multiple bonding devices with differing options, it is 1109preferrable to use bonding parameters exported by sysfs, documented in the 1110section below. 1111 1112 For versions of bonding without sysfs support, the only means to 1113provide multiple instances of bonding with differing options is to load 1114the bonding driver multiple times. Note that current versions of the 1115sysconfig network initialization scripts handle this automatically; if 1116your distro uses these scripts, no special action is needed. See the 1117section Configuring Bonding Devices, above, if you're not sure about your 1118network initialization scripts. 1119 1120 To load multiple instances of the module, it is necessary to 1121specify a different name for each instance (the module loading system 1122requires that every loaded module, even multiple instances of the same 1123module, have a unique name). This is accomplished by supplying multiple 1124sets of bonding options in /etc/modprobe.conf, for example: 1125 1126alias bond0 bonding 1127options bond0 -o bond0 mode=balance-rr miimon=100 1128 1129alias bond1 bonding 1130options bond1 -o bond1 mode=balance-alb miimon=50 1131 1132 will load the bonding module two times. The first instance is 1133named "bond0" and creates the bond0 device in balance-rr mode with an 1134miimon of 100. The second instance is named "bond1" and creates the 1135bond1 device in balance-alb mode with an miimon of 50. 1136 1137 In some circumstances (typically with older distributions), 1138the above does not work, and the second bonding instance never sees 1139its options. In that case, the second options line can be substituted 1140as follows: 1141 1142install bond1 /sbin/modprobe --ignore-install bonding -o bond1 \ 1143 mode=balance-alb miimon=50 1144 1145 This may be repeated any number of times, specifying a new and 1146unique name in place of bond1 for each subsequent instance. 1147 1148 It has been observed that some Red Hat supplied kernels are unable 1149to rename modules at load time (the "-o bond1" part). Attempts to pass 1150that option to modprobe will produce an "Operation not permitted" error. 1151This has been reported on some Fedora Core kernels, and has been seen on 1152RHEL 4 as well. On kernels exhibiting this problem, it will be impossible 1153to configure multiple bonds with differing parameters (as they are older 1154kernels, and also lack sysfs support). 1155 11563.4 Configuring Bonding Manually via Sysfs 1157------------------------------------------ 1158 1159 Starting with version 3.0.0, Channel Bonding may be configured 1160via the sysfs interface. This interface allows dynamic configuration 1161of all bonds in the system without unloading the module. It also 1162allows for adding and removing bonds at runtime. Ifenslave is no 1163longer required, though it is still supported. 1164 1165 Use of the sysfs interface allows you to use multiple bonds 1166with different configurations without having to reload the module. 1167It also allows you to use multiple, differently configured bonds when 1168bonding is compiled into the kernel. 1169 1170 You must have the sysfs filesystem mounted to configure 1171bonding this way. The examples in this document assume that you 1172are using the standard mount point for sysfs, e.g. /sys. If your 1173sysfs filesystem is mounted elsewhere, you will need to adjust the 1174example paths accordingly. 1175 1176Creating and Destroying Bonds 1177----------------------------- 1178To add a new bond foo: 1179# echo +foo > /sys/class/net/bonding_masters 1180 1181To remove an existing bond bar: 1182# echo -bar > /sys/class/net/bonding_masters 1183 1184To show all existing bonds: 1185# cat /sys/class/net/bonding_masters 1186 1187NOTE: due to 4K size limitation of sysfs files, this list may be 1188truncated if you have more than a few hundred bonds. This is unlikely 1189to occur under normal operating conditions. 1190 1191Adding and Removing Slaves 1192-------------------------- 1193 Interfaces may be enslaved to a bond using the file 1194/sys/class/net/<bond>/bonding/slaves. The semantics for this file 1195are the same as for the bonding_masters file. 1196 1197To enslave interface eth0 to bond bond0: 1198# ifconfig bond0 up 1199# echo +eth0 > /sys/class/net/bond0/bonding/slaves 1200 1201To free slave eth0 from bond bond0: 1202# echo -eth0 > /sys/class/net/bond0/bonding/slaves 1203 1204 When an interface is enslaved to a bond, symlinks between the 1205two are created in the sysfs filesystem. In this case, you would get 1206/sys/class/net/bond0/slave_eth0 pointing to /sys/class/net/eth0, and 1207/sys/class/net/eth0/master pointing to /sys/class/net/bond0. 1208 1209 This means that you can tell quickly whether or not an 1210interface is enslaved by looking for the master symlink. Thus: 1211# echo -eth0 > /sys/class/net/eth0/master/bonding/slaves 1212will free eth0 from whatever bond it is enslaved to, regardless of 1213the name of the bond interface. 1214 1215Changing a Bond's Configuration 1216------------------------------- 1217 Each bond may be configured individually by manipulating the 1218files located in /sys/class/net/<bond name>/bonding 1219 1220 The names of these files correspond directly with the command- 1221line parameters described elsewhere in this file, and, with the 1222exception of arp_ip_target, they accept the same values. To see the 1223current setting, simply cat the appropriate file. 1224 1225 A few examples will be given here; for specific usage 1226guidelines for each parameter, see the appropriate section in this 1227document. 1228 1229To configure bond0 for balance-alb mode: 1230# ifconfig bond0 down 1231# echo 6 > /sys/class/net/bond0/bonding/mode 1232 - or - 1233# echo balance-alb > /sys/class/net/bond0/bonding/mode 1234 NOTE: The bond interface must be down before the mode can be 1235changed. 1236 1237To enable MII monitoring on bond0 with a 1 second interval: 1238# echo 1000 > /sys/class/net/bond0/bonding/miimon 1239 NOTE: If ARP monitoring is enabled, it will disabled when MII 1240monitoring is enabled, and vice-versa. 1241 1242To add ARP targets: 1243# echo +192.168.0.100 > /sys/class/net/bond0/bonding/arp_ip_target 1244# echo +192.168.0.101 > /sys/class/net/bond0/bonding/arp_ip_target 1245 NOTE: up to 10 target addresses may be specified. 1246 1247To remove an ARP target: 1248# echo -192.168.0.100 > /sys/class/net/bond0/bonding/arp_ip_target 1249 1250Example Configuration 1251--------------------- 1252 We begin with the same example that is shown in section 3.3, 1253executed with sysfs, and without using ifenslave. 1254 1255 To make a simple bond of two e100 devices (presumed to be eth0 1256and eth1), and have it persist across reboots, edit the appropriate 1257file (/etc/init.d/boot.local or /etc/rc.d/rc.local), and add the 1258following: 1259 1260modprobe bonding 1261modprobe e100 1262echo balance-alb > /sys/class/net/bond0/bonding/mode 1263ifconfig bond0 192.168.1.1 netmask 255.255.255.0 up 1264echo 100 > /sys/class/net/bond0/bonding/miimon 1265echo +eth0 > /sys/class/net/bond0/bonding/slaves 1266echo +eth1 > /sys/class/net/bond0/bonding/slaves 1267 1268 To add a second bond, with two e1000 interfaces in 1269active-backup mode, using ARP monitoring, add the following lines to 1270your init script: 1271 1272modprobe e1000 1273echo +bond1 > /sys/class/net/bonding_masters 1274echo active-backup > /sys/class/net/bond1/bonding/mode 1275ifconfig bond1 192.168.2.1 netmask 255.255.255.0 up 1276echo +192.168.2.100 /sys/class/net/bond1/bonding/arp_ip_target 1277echo 2000 > /sys/class/net/bond1/bonding/arp_interval 1278echo +eth2 > /sys/class/net/bond1/bonding/slaves 1279echo +eth3 > /sys/class/net/bond1/bonding/slaves 1280 1281 12824. Querying Bonding Configuration 1283================================= 1284 12854.1 Bonding Configuration 1286------------------------- 1287 1288 Each bonding device has a read-only file residing in the 1289/proc/net/bonding directory. The file contents include information 1290about the bonding configuration, options and state of each slave. 1291 1292 For example, the contents of /proc/net/bonding/bond0 after the 1293driver is loaded with parameters of mode=0 and miimon=1000 is 1294generally as follows: 1295 1296 Ethernet Channel Bonding Driver: 2.6.1 (October 29, 2004) 1297 Bonding Mode: load balancing (round-robin) 1298 Currently Active Slave: eth0 1299 MII Status: up 1300 MII Polling Interval (ms): 1000 1301 Up Delay (ms): 0 1302 Down Delay (ms): 0 1303 1304 Slave Interface: eth1 1305 MII Status: up 1306 Link Failure Count: 1 1307 1308 Slave Interface: eth0 1309 MII Status: up 1310 Link Failure Count: 1 1311 1312 The precise format and contents will change depending upon the 1313bonding configuration, state, and version of the bonding driver. 1314 13154.2 Network configuration 1316------------------------- 1317 1318 The network configuration can be inspected using the ifconfig 1319command. Bonding devices will have the MASTER flag set; Bonding slave 1320devices will have the SLAVE flag set. The ifconfig output does not 1321contain information on which slaves are associated with which masters. 1322 1323 In the example below, the bond0 interface is the master 1324(MASTER) while eth0 and eth1 are slaves (SLAVE). Notice all slaves of 1325bond0 have the same MAC address (HWaddr) as bond0 for all modes except 1326TLB and ALB that require a unique MAC address for each slave. 1327 1328# /sbin/ifconfig 1329bond0 Link encap:Ethernet HWaddr 00:C0:F0:1F:37:B4 1330 inet addr:XXX.XXX.XXX.YYY Bcast:XXX.XXX.XXX.255 Mask:255.255.252.0 1331 UP BROADCAST RUNNING MASTER MULTICAST MTU:1500 Metric:1 1332 RX packets:7224794 errors:0 dropped:0 overruns:0 frame:0 1333 TX packets:3286647 errors:1 dropped:0 overruns:1 carrier:0 1334 collisions:0 txqueuelen:0 1335 1336eth0 Link encap:Ethernet HWaddr 00:C0:F0:1F:37:B4 1337 UP BROADCAST RUNNING SLAVE MULTICAST MTU:1500 Metric:1 1338 RX packets:3573025 errors:0 dropped:0 overruns:0 frame:0 1339 TX packets:1643167 errors:1 dropped:0 overruns:1 carrier:0 1340 collisions:0 txqueuelen:100 1341 Interrupt:10 Base address:0x1080 1342 1343eth1 Link encap:Ethernet HWaddr 00:C0:F0:1F:37:B4 1344 UP BROADCAST RUNNING SLAVE MULTICAST MTU:1500 Metric:1 1345 RX packets:3651769 errors:0 dropped:0 overruns:0 frame:0 1346 TX packets:1643480 errors:0 dropped:0 overruns:0 carrier:0 1347 collisions:0 txqueuelen:100 1348 Interrupt:9 Base address:0x1400 1349 13505. Switch Configuration 1351======================= 1352 1353 For this section, "switch" refers to whatever system the 1354bonded devices are directly connected to (i.e., where the other end of 1355the cable plugs into). This may be an actual dedicated switch device, 1356or it may be another regular system (e.g., another computer running 1357Linux), 1358 1359 The active-backup, balance-tlb and balance-alb modes do not 1360require any specific configuration of the switch. 1361 1362 The 802.3ad mode requires that the switch have the appropriate 1363ports configured as an 802.3ad aggregation. The precise method used 1364to configure this varies from switch to switch, but, for example, a 1365Cisco 3550 series switch requires that the appropriate ports first be 1366grouped together in a single etherchannel instance, then that 1367etherchannel is set to mode "lacp" to enable 802.3ad (instead of 1368standard EtherChannel). 1369 1370 The balance-rr, balance-xor and broadcast modes generally 1371require that the switch have the appropriate ports grouped together. 1372The nomenclature for such a group differs between switches, it may be 1373called an "etherchannel" (as in the Cisco example, above), a "trunk 1374group" or some other similar variation. For these modes, each switch 1375will also have its own configuration options for the switch's transmit 1376policy to the bond. Typical choices include XOR of either the MAC or 1377IP addresses. The transmit policy of the two peers does not need to 1378match. For these three modes, the bonding mode really selects a 1379transmit policy for an EtherChannel group; all three will interoperate 1380with another EtherChannel group. 1381 1382 13836. 802.1q VLAN Support 1384====================== 1385 1386 It is possible to configure VLAN devices over a bond interface 1387using the 8021q driver. However, only packets coming from the 8021q 1388driver and passing through bonding will be tagged by default. Self 1389generated packets, for example, bonding's learning packets or ARP 1390packets generated by either ALB mode or the ARP monitor mechanism, are 1391tagged internally by bonding itself. As a result, bonding must 1392"learn" the VLAN IDs configured above it, and use those IDs to tag 1393self generated packets. 1394 1395 For reasons of simplicity, and to support the use of adapters 1396that can do VLAN hardware acceleration offloading, the bonding 1397interface declares itself as fully hardware offloading capable, it gets 1398the add_vid/kill_vid notifications to gather the necessary 1399information, and it propagates those actions to the slaves. In case 1400of mixed adapter types, hardware accelerated tagged packets that 1401should go through an adapter that is not offloading capable are 1402"un-accelerated" by the bonding driver so the VLAN tag sits in the 1403regular location. 1404 1405 VLAN interfaces *must* be added on top of a bonding interface 1406only after enslaving at least one slave. The bonding interface has a 1407hardware address of 00:00:00:00:00:00 until the first slave is added. 1408If the VLAN interface is created prior to the first enslavement, it 1409would pick up the all-zeroes hardware address. Once the first slave 1410is attached to the bond, the bond device itself will pick up the 1411slave's hardware address, which is then available for the VLAN device. 1412 1413 Also, be aware that a similar problem can occur if all slaves 1414are released from a bond that still has one or more VLAN interfaces on 1415top of it. When a new slave is added, the bonding interface will 1416obtain its hardware address from the first slave, which might not 1417match the hardware address of the VLAN interfaces (which was 1418ultimately copied from an earlier slave). 1419 1420 There are two methods to insure that the VLAN device operates 1421with the correct hardware address if all slaves are removed from a 1422bond interface: 1423 1424 1. Remove all VLAN interfaces then recreate them 1425 1426 2. Set the bonding interface's hardware address so that it 1427matches the hardware address of the VLAN interfaces. 1428 1429 Note that changing a VLAN interface's HW address would set the 1430underlying device -- i.e. the bonding interface -- to promiscuous 1431mode, which might not be what you want. 1432 1433 14347. Link Monitoring 1435================== 1436 1437 The bonding driver at present supports two schemes for 1438monitoring a slave device's link state: the ARP monitor and the MII 1439monitor. 1440 1441 At the present time, due to implementation restrictions in the 1442bonding driver itself, it is not possible to enable both ARP and MII 1443monitoring simultaneously. 1444 14457.1 ARP Monitor Operation 1446------------------------- 1447 1448 The ARP monitor operates as its name suggests: it sends ARP 1449queries to one or more designated peer systems on the network, and 1450uses the response as an indication that the link is operating. This 1451gives some assurance that traffic is actually flowing to and from one 1452or more peers on the local network. 1453 1454 The ARP monitor relies on the device driver itself to verify 1455that traffic is flowing. In particular, the driver must keep up to 1456date the last receive time, dev->last_rx, and transmit start time, 1457dev->trans_start. If these are not updated by the driver, then the 1458ARP monitor will immediately fail any slaves using that driver, and 1459those slaves will stay down. If networking monitoring (tcpdump, etc) 1460shows the ARP requests and replies on the network, then it may be that 1461your device driver is not updating last_rx and trans_start. 1462 14637.2 Configuring Multiple ARP Targets 1464------------------------------------ 1465 1466 While ARP monitoring can be done with just one target, it can 1467be useful in a High Availability setup to have several targets to 1468monitor. In the case of just one target, the target itself may go 1469down or have a problem making it unresponsive to ARP requests. Having 1470an additional target (or several) increases the reliability of the ARP 1471monitoring. 1472 1473 Multiple ARP targets must be separated by commas as follows: 1474 1475# example options for ARP monitoring with three targets 1476alias bond0 bonding 1477options bond0 arp_interval=60 arp_ip_target=192.168.0.1,192.168.0.3,192.168.0.9 1478 1479 For just a single target the options would resemble: 1480 1481# example options for ARP monitoring with one target 1482alias bond0 bonding 1483options bond0 arp_interval=60 arp_ip_target=192.168.0.100 1484 1485 14867.3 MII Monitor Operation 1487------------------------- 1488 1489 The MII monitor monitors only the carrier state of the local 1490network interface. It accomplishes this in one of three ways: by 1491depending upon the device driver to maintain its carrier state, by 1492querying the device's MII registers, or by making an ethtool query to 1493the device. 1494 1495 If the use_carrier module parameter is 1 (the default value), 1496then the MII monitor will rely on the driver for carrier state 1497information (via the netif_carrier subsystem). As explained in the 1498use_carrier parameter information, above, if the MII monitor fails to 1499detect carrier loss on the device (e.g., when the cable is physically 1500disconnected), it may be that the driver does not support 1501netif_carrier. 1502 1503 If use_carrier is 0, then the MII monitor will first query the 1504device's (via ioctl) MII registers and check the link state. If that 1505request fails (not just that it returns carrier down), then the MII 1506monitor will make an ethtool ETHOOL_GLINK request to attempt to obtain 1507the same information. If both methods fail (i.e., the driver either 1508does not support or had some error in processing both the MII register 1509and ethtool requests), then the MII monitor will assume the link is 1510up. 1511 15128. Potential Sources of Trouble 1513=============================== 1514 15158.1 Adventures in Routing 1516------------------------- 1517 1518 When bonding is configured, it is important that the slave 1519devices not have routes that supersede routes of the master (or, 1520generally, not have routes at all). For example, suppose the bonding 1521device bond0 has two slaves, eth0 and eth1, and the routing table is 1522as follows: 1523 1524Kernel IP routing table 1525Destination Gateway Genmask Flags MSS Window irtt Iface 152610.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 eth0 152710.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 eth1 152810.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 bond0 1529127.0.0.0 0.0.0.0 255.0.0.0 U 40 0 0 lo 1530 1531 This routing configuration will likely still update the 1532receive/transmit times in the driver (needed by the ARP monitor), but 1533may bypass the bonding driver (because outgoing traffic to, in this 1534case, another host on network 10 would use eth0 or eth1 before bond0). 1535 1536 The ARP monitor (and ARP itself) may become confused by this 1537configuration, because ARP requests (generated by the ARP monitor) 1538will be sent on one interface (bond0), but the corresponding reply 1539will arrive on a different interface (eth0). This reply looks to ARP 1540as an unsolicited ARP reply (because ARP matches replies on an 1541interface basis), and is discarded. The MII monitor is not affected 1542by the state of the routing table. 1543 1544 The solution here is simply to insure that slaves do not have 1545routes of their own, and if for some reason they must, those routes do 1546not supersede routes of their master. This should generally be the 1547case, but unusual configurations or errant manual or automatic static 1548route additions may cause trouble. 1549 15508.2 Ethernet Device Renaming 1551---------------------------- 1552 1553 On systems with network configuration scripts that do not 1554associate physical devices directly with network interface names (so 1555that the same physical device always has the same "ethX" name), it may 1556be necessary to add some special logic to either /etc/modules.conf or 1557/etc/modprobe.conf (depending upon which is installed on the system). 1558 1559 For example, given a modules.conf containing the following: 1560 1561alias bond0 bonding 1562options bond0 mode=some-mode miimon=50 1563alias eth0 tg3 1564alias eth1 tg3 1565alias eth2 e1000 1566alias eth3 e1000 1567 1568 If neither eth0 and eth1 are slaves to bond0, then when the 1569bond0 interface comes up, the devices may end up reordered. This 1570happens because bonding is loaded first, then its slave device's 1571drivers are loaded next. Since no other drivers have been loaded, 1572when the e1000 driver loads, it will receive eth0 and eth1 for its 1573devices, but the bonding configuration tries to enslave eth2 and eth3 1574(which may later be assigned to the tg3 devices). 1575 1576 Adding the following: 1577 1578add above bonding e1000 tg3 1579 1580 causes modprobe to load e1000 then tg3, in that order, when 1581bonding is loaded. This command is fully documented in the 1582modules.conf manual page. 1583 1584 On systems utilizing modprobe.conf (or modprobe.conf.local), 1585an equivalent problem can occur. In this case, the following can be 1586added to modprobe.conf (or modprobe.conf.local, as appropriate), as 1587follows (all on one line; it has been split here for clarity): 1588 1589install bonding /sbin/modprobe tg3; /sbin/modprobe e1000; 1590 /sbin/modprobe --ignore-install bonding 1591 1592 This will, when loading the bonding module, rather than 1593performing the normal action, instead execute the provided command. 1594This command loads the device drivers in the order needed, then calls 1595modprobe with --ignore-install to cause the normal action to then take 1596place. Full documentation on this can be found in the modprobe.conf 1597and modprobe manual pages. 1598 15998.3. Painfully Slow Or No Failed Link Detection By Miimon 1600--------------------------------------------------------- 1601 1602 By default, bonding enables the use_carrier option, which 1603instructs bonding to trust the driver to maintain carrier state. 1604 1605 As discussed in the options section, above, some drivers do 1606not support the netif_carrier_on/_off link state tracking system. 1607With use_carrier enabled, bonding will always see these links as up, 1608regardless of their actual state. 1609 1610 Additionally, other drivers do support netif_carrier, but do 1611not maintain it in real time, e.g., only polling the link state at 1612some fixed interval. In this case, miimon will detect failures, but 1613only after some long period of time has expired. If it appears that 1614miimon is very slow in detecting link failures, try specifying 1615use_carrier=0 to see if that improves the failure detection time. If 1616it does, then it may be that the driver checks the carrier state at a 1617fixed interval, but does not cache the MII register values (so the 1618use_carrier=0 method of querying the registers directly works). If 1619use_carrier=0 does not improve the failover, then the driver may cache 1620the registers, or the problem may be elsewhere. 1621 1622 Also, remember that miimon only checks for the device's 1623carrier state. It has no way to determine the state of devices on or 1624beyond other ports of a switch, or if a switch is refusing to pass 1625traffic while still maintaining carrier on. 1626 16279. SNMP agents 1628=============== 1629 1630 If running SNMP agents, the bonding driver should be loaded 1631before any network drivers participating in a bond. This requirement 1632is due to the interface index (ipAdEntIfIndex) being associated to 1633the first interface found with a given IP address. That is, there is 1634only one ipAdEntIfIndex for each IP address. For example, if eth0 and 1635eth1 are slaves of bond0 and the driver for eth0 is loaded before the 1636bonding driver, the interface for the IP address will be associated 1637with the eth0 interface. This configuration is shown below, the IP 1638address 192.168.1.1 has an interface index of 2 which indexes to eth0 1639in the ifDescr table (ifDescr.2). 1640 1641 interfaces.ifTable.ifEntry.ifDescr.1 = lo 1642 interfaces.ifTable.ifEntry.ifDescr.2 = eth0 1643 interfaces.ifTable.ifEntry.ifDescr.3 = eth1 1644 interfaces.ifTable.ifEntry.ifDescr.4 = eth2 1645 interfaces.ifTable.ifEntry.ifDescr.5 = eth3 1646 interfaces.ifTable.ifEntry.ifDescr.6 = bond0 1647 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.10.10.10 = 5 1648 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.192.168.1.1 = 2 1649 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.74.20.94 = 4 1650 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.127.0.0.1 = 1 1651 1652 This problem is avoided by loading the bonding driver before 1653any network drivers participating in a bond. Below is an example of 1654loading the bonding driver first, the IP address 192.168.1.1 is 1655correctly associated with ifDescr.2. 1656 1657 interfaces.ifTable.ifEntry.ifDescr.1 = lo 1658 interfaces.ifTable.ifEntry.ifDescr.2 = bond0 1659 interfaces.ifTable.ifEntry.ifDescr.3 = eth0 1660 interfaces.ifTable.ifEntry.ifDescr.4 = eth1 1661 interfaces.ifTable.ifEntry.ifDescr.5 = eth2 1662 interfaces.ifTable.ifEntry.ifDescr.6 = eth3 1663 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.10.10.10 = 6 1664 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.192.168.1.1 = 2 1665 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.74.20.94 = 5 1666 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.127.0.0.1 = 1 1667 1668 While some distributions may not report the interface name in 1669ifDescr, the association between the IP address and IfIndex remains 1670and SNMP functions such as Interface_Scan_Next will report that 1671association. 1672 167310. Promiscuous mode 1674==================== 1675 1676 When running network monitoring tools, e.g., tcpdump, it is 1677common to enable promiscuous mode on the device, so that all traffic 1678is seen (instead of seeing only traffic destined for the local host). 1679The bonding driver handles promiscuous mode changes to the bonding 1680master device (e.g., bond0), and propagates the setting to the slave 1681devices. 1682 1683 For the balance-rr, balance-xor, broadcast, and 802.3ad modes, 1684the promiscuous mode setting is propagated to all slaves. 1685 1686 For the active-backup, balance-tlb and balance-alb modes, the 1687promiscuous mode setting is propagated only to the active slave. 1688 1689 For balance-tlb mode, the active slave is the slave currently 1690receiving inbound traffic. 1691 1692 For balance-alb mode, the active slave is the slave used as a 1693"primary." This slave is used for mode-specific control traffic, for 1694sending to peers that are unassigned or if the load is unbalanced. 1695 1696 For the active-backup, balance-tlb and balance-alb modes, when 1697the active slave changes (e.g., due to a link failure), the 1698promiscuous setting will be propagated to the new active slave. 1699 170011. Configuring Bonding for High Availability 1701============================================= 1702 1703 High Availability refers to configurations that provide 1704maximum network availability by having redundant or backup devices, 1705links or switches between the host and the rest of the world. The 1706goal is to provide the maximum availability of network connectivity 1707(i.e., the network always works), even though other configurations 1708could provide higher throughput. 1709 171011.1 High Availability in a Single Switch Topology 1711-------------------------------------------------- 1712 1713 If two hosts (or a host and a single switch) are directly 1714connected via multiple physical links, then there is no availability 1715penalty to optimizing for maximum bandwidth. In this case, there is 1716only one switch (or peer), so if it fails, there is no alternative 1717access to fail over to. Additionally, the bonding load balance modes 1718support link monitoring of their members, so if individual links fail, 1719the load will be rebalanced across the remaining devices. 1720 1721 See Section 13, "Configuring Bonding for Maximum Throughput" 1722for information on configuring bonding with one peer device. 1723 172411.2 High Availability in a Multiple Switch Topology 1725---------------------------------------------------- 1726 1727 With multiple switches, the configuration of bonding and the 1728network changes dramatically. In multiple switch topologies, there is 1729a trade off between network availability and usable bandwidth. 1730 1731 Below is a sample network, configured to maximize the 1732availability of the network: 1733 1734 | | 1735 |port3 port3| 1736 +-----+----+ +-----+----+ 1737 | |port2 ISL port2| | 1738 | switch A +--------------------------+ switch B | 1739 | | | | 1740 +-----+----+ +-----++---+ 1741 |port1 port1| 1742 | +-------+ | 1743 +-------------+ host1 +---------------+ 1744 eth0 +-------+ eth1 1745 1746 In this configuration, there is a link between the two 1747switches (ISL, or inter switch link), and multiple ports connecting to 1748the outside world ("port3" on each switch). There is no technical 1749reason that this could not be extended to a third switch. 1750 175111.2.1 HA Bonding Mode Selection for Multiple Switch Topology 1752------------------------------------------------------------- 1753 1754 In a topology such as the example above, the active-backup and 1755broadcast modes are the only useful bonding modes when optimizing for 1756availability; the other modes require all links to terminate on the 1757same peer for them to behave rationally. 1758 1759active-backup: This is generally the preferred mode, particularly if 1760 the switches have an ISL and play together well. If the 1761 network configuration is such that one switch is specifically 1762 a backup switch (e.g., has lower capacity, higher cost, etc), 1763 then the primary option can be used to insure that the 1764 preferred link is always used when it is available. 1765 1766broadcast: This mode is really a special purpose mode, and is suitable 1767 only for very specific needs. For example, if the two 1768 switches are not connected (no ISL), and the networks beyond 1769 them are totally independent. In this case, if it is 1770 necessary for some specific one-way traffic to reach both 1771 independent networks, then the broadcast mode may be suitable. 1772 177311.2.2 HA Link Monitoring Selection for Multiple Switch Topology 1774---------------------------------------------------------------- 1775 1776 The choice of link monitoring ultimately depends upon your 1777switch. If the switch can reliably fail ports in response to other 1778failures, then either the MII or ARP monitors should work. For 1779example, in the above example, if the "port3" link fails at the remote 1780end, the MII monitor has no direct means to detect this. The ARP 1781monitor could be configured with a target at the remote end of port3, 1782thus detecting that failure without switch support. 1783 1784 In general, however, in a multiple switch topology, the ARP 1785monitor can provide a higher level of reliability in detecting end to 1786end connectivity failures (which may be caused by the failure of any 1787individual component to pass traffic for any reason). Additionally, 1788the ARP monitor should be configured with multiple targets (at least 1789one for each switch in the network). This will insure that, 1790regardless of which switch is active, the ARP monitor has a suitable 1791target to query. 1792 1793 Note, also, that of late many switches now support a functionality 1794generally referred to as "trunk failover." This is a feature of the 1795switch that causes the link state of a particular switch port to be set 1796down (or up) when the state of another switch port goes down (or up). 1797It's purpose is to propogate link failures from logically "exterior" ports 1798to the logically "interior" ports that bonding is able to monitor via 1799miimon. Availability and configuration for trunk failover varies by 1800switch, but this can be a viable alternative to the ARP monitor when using 1801suitable switches. 1802 180312. Configuring Bonding for Maximum Throughput 1804============================================== 1805 180612.1 Maximizing Throughput in a Single Switch Topology 1807------------------------------------------------------ 1808 1809 In a single switch configuration, the best method to maximize 1810throughput depends upon the application and network environment. The 1811various load balancing modes each have strengths and weaknesses in 1812different environments, as detailed below. 1813 1814 For this discussion, we will break down the topologies into 1815two categories. Depending upon the destination of most traffic, we 1816categorize them into either "gatewayed" or "local" configurations. 1817 1818 In a gatewayed configuration, the "switch" is acting primarily 1819as a router, and the majority of traffic passes through this router to 1820other networks. An example would be the following: 1821 1822 1823 +----------+ +----------+ 1824 | |eth0 port1| | to other networks 1825 | Host A +---------------------+ router +-------------------> 1826 | +---------------------+ | Hosts B and C are out 1827 | |eth1 port2| | here somewhere 1828 +----------+ +----------+ 1829 1830 The router may be a dedicated router device, or another host 1831acting as a gateway. For our discussion, the important point is that 1832the majority of traffic from Host A will pass through the router to 1833some other network before reaching its final destination. 1834 1835 In a gatewayed network configuration, although Host A may 1836communicate with many other systems, all of its traffic will be sent 1837and received via one other peer on the local network, the router. 1838 1839 Note that the case of two systems connected directly via 1840multiple physical links is, for purposes of configuring bonding, the 1841same as a gatewayed configuration. In that case, it happens that all 1842traffic is destined for the "gateway" itself, not some other network 1843beyond the gateway. 1844 1845 In a local configuration, the "switch" is acting primarily as 1846a switch, and the majority of traffic passes through this switch to 1847reach other stations on the same network. An example would be the 1848following: 1849 1850 +----------+ +----------+ +--------+ 1851 | |eth0 port1| +-------+ Host B | 1852 | Host A +------------+ switch |port3 +--------+ 1853 | +------------+ | +--------+ 1854 | |eth1 port2| +------------------+ Host C | 1855 +----------+ +----------+port4 +--------+ 1856 1857 1858 Again, the switch may be a dedicated switch device, or another 1859host acting as a gateway. For our discussion, the important point is 1860that the majority of traffic from Host A is destined for other hosts 1861on the same local network (Hosts B and C in the above example). 1862 1863 In summary, in a gatewayed configuration, traffic to and from 1864the bonded device will be to the same MAC level peer on the network 1865(the gateway itself, i.e., the router), regardless of its final 1866destination. In a local configuration, traffic flows directly to and 1867from the final destinations, thus, each destination (Host B, Host C) 1868will be addressed directly by their individual MAC addresses. 1869 1870 This distinction between a gatewayed and a local network 1871configuration is important because many of the load balancing modes 1872available use the MAC addresses of the local network source and 1873destination to make load balancing decisions. The behavior of each 1874mode is described below. 1875 1876 187712.1.1 MT Bonding Mode Selection for Single Switch Topology 1878----------------------------------------------------------- 1879 1880 This configuration is the easiest to set up and to understand, 1881although you will have to decide which bonding mode best suits your 1882needs. The trade offs for each mode are detailed below: 1883 1884balance-rr: This mode is the only mode that will permit a single 1885 TCP/IP connection to stripe traffic across multiple 1886 interfaces. It is therefore the only mode that will allow a 1887 single TCP/IP stream to utilize more than one interface's 1888 worth of throughput. This comes at a cost, however: the 1889 striping generally results in peer systems receiving packets out 1890 of order, causing TCP/IP's congestion control system to kick 1891 in, often by retransmitting segments. 1892 1893 It is possible to adjust TCP/IP's congestion limits by 1894 altering the net.ipv4.tcp_reordering sysctl parameter. The 1895 usual default value is 3, and the maximum useful value is 127. 1896 For a four interface balance-rr bond, expect that a single 1897 TCP/IP stream will utilize no more than approximately 2.3 1898 interface's worth of throughput, even after adjusting 1899 tcp_reordering. 1900 1901 Note that the fraction of packets that will be delivered out of 1902 order is highly variable, and is unlikely to be zero. The level 1903 of reordering depends upon a variety of factors, including the 1904 networking interfaces, the switch, and the topology of the 1905 configuration. Speaking in general terms, higher speed network 1906 cards produce more reordering (due to factors such as packet 1907 coalescing), and a "many to many" topology will reorder at a 1908 higher rate than a "many slow to one fast" configuration. 1909 1910 Many switches do not support any modes that stripe traffic 1911 (instead choosing a port based upon IP or MAC level addresses); 1912 for those devices, traffic for a particular connection flowing 1913 through the switch to a balance-rr bond will not utilize greater 1914 than one interface's worth of bandwidth. 1915 1916 If you are utilizing protocols other than TCP/IP, UDP for 1917 example, and your application can tolerate out of order 1918 delivery, then this mode can allow for single stream datagram 1919 performance that scales near linearly as interfaces are added 1920 to the bond. 1921 1922 This mode requires the switch to have the appropriate ports 1923 configured for "etherchannel" or "trunking." 1924 1925active-backup: There is not much advantage in this network topology to 1926 the active-backup mode, as the inactive backup devices are all 1927 connected to the same peer as the primary. In this case, a 1928 load balancing mode (with link monitoring) will provide the 1929 same level of network availability, but with increased 1930 available bandwidth. On the plus side, active-backup mode 1931 does not require any configuration of the switch, so it may 1932 have value if the hardware available does not support any of 1933 the load balance modes. 1934 1935balance-xor: This mode will limit traffic such that packets destined 1936 for specific peers will always be sent over the same 1937 interface. Since the destination is determined by the MAC 1938 addresses involved, this mode works best in a "local" network 1939 configuration (as described above), with destinations all on 1940 the same local network. This mode is likely to be suboptimal 1941 if all your traffic is passed through a single router (i.e., a 1942 "gatewayed" network configuration, as described above). 1943 1944 As with balance-rr, the switch ports need to be configured for 1945 "etherchannel" or "trunking." 1946 1947broadcast: Like active-backup, there is not much advantage to this 1948 mode in this type of network topology. 1949 1950802.3ad: This mode can be a good choice for this type of network 1951 topology. The 802.3ad mode is an IEEE standard, so all peers 1952 that implement 802.3ad should interoperate well. The 802.3ad 1953 protocol includes automatic configuration of the aggregates, 1954 so minimal manual configuration of the switch is needed 1955 (typically only to designate that some set of devices is 1956 available for 802.3ad). The 802.3ad standard also mandates 1957 that frames be delivered in order (within certain limits), so 1958 in general single connections will not see misordering of 1959 packets. The 802.3ad mode does have some drawbacks: the 1960 standard mandates that all devices in the aggregate operate at 1961 the same speed and duplex. Also, as with all bonding load 1962 balance modes other than balance-rr, no single connection will 1963 be able to utilize more than a single interface's worth of 1964 bandwidth. 1965 1966 Additionally, the linux bonding 802.3ad implementation 1967 distributes traffic by peer (using an XOR of MAC addresses), 1968 so in a "gatewayed" configuration, all outgoing traffic will 1969 generally use the same device. Incoming traffic may also end 1970 up on a single device, but that is dependent upon the 1971 balancing policy of the peer's 8023.ad implementation. In a 1972 "local" configuration, traffic will be distributed across the 1973 devices in the bond. 1974 1975 Finally, the 802.3ad mode mandates the use of the MII monitor, 1976 therefore, the ARP monitor is not available in this mode. 1977 1978balance-tlb: The balance-tlb mode balances outgoing traffic by peer. 1979 Since the balancing is done according to MAC address, in a 1980 "gatewayed" configuration (as described above), this mode will 1981 send all traffic across a single device. However, in a 1982 "local" network configuration, this mode balances multiple 1983 local network peers across devices in a vaguely intelligent 1984 manner (not a simple XOR as in balance-xor or 802.3ad mode), 1985 so that mathematically unlucky MAC addresses (i.e., ones that 1986 XOR to the same value) will not all "bunch up" on a single 1987 interface. 1988 1989 Unlike 802.3ad, interfaces may be of differing speeds, and no 1990 special switch configuration is required. On the down side, 1991 in this mode all incoming traffic arrives over a single 1992 interface, this mode requires certain ethtool support in the 1993 network device driver of the slave interfaces, and the ARP 1994 monitor is not available. 1995 1996balance-alb: This mode is everything that balance-tlb is, and more. 1997 It has all of the features (and restrictions) of balance-tlb, 1998 and will also balance incoming traffic from local network 1999 peers (as described in the Bonding Module Options section, 2000 above). 2001 2002 The only additional down side to this mode is that the network 2003 device driver must support changing the hardware address while 2004 the device is open. 2005 200612.1.2 MT Link Monitoring for Single Switch Topology 2007---------------------------------------------------- 2008 2009 The choice of link monitoring may largely depend upon which 2010mode you choose to use. The more advanced load balancing modes do not 2011support the use of the ARP monitor, and are thus restricted to using 2012the MII monitor (which does not provide as high a level of end to end 2013assurance as the ARP monitor). 2014 201512.2 Maximum Throughput in a Multiple Switch Topology 2016----------------------------------------------------- 2017 2018 Multiple switches may be utilized to optimize for throughput 2019when they are configured in parallel as part of an isolated network 2020between two or more systems, for example: 2021 2022 +-----------+ 2023 | Host A | 2024 +-+---+---+-+ 2025 | | | 2026 +--------+ | +---------+ 2027 | | | 2028 +------+---+ +-----+----+ +-----+----+ 2029 | Switch A | | Switch B | | Switch C | 2030 +------+---+ +-----+----+ +-----+----+ 2031 | | | 2032 +--------+ | +---------+ 2033 | | | 2034 +-+---+---+-+ 2035 | Host B | 2036 +-----------+ 2037 2038 In this configuration, the switches are isolated from one 2039another. One reason to employ a topology such as this is for an 2040isolated network with many hosts (a cluster configured for high 2041performance, for example), using multiple smaller switches can be more 2042cost effective than a single larger switch, e.g., on a network with 24 2043hosts, three 24 port switches can be significantly less expensive than 2044a single 72 port switch. 2045 2046 If access beyond the network is required, an individual host 2047can be equipped with an additional network device connected to an 2048external network; this host then additionally acts as a gateway. 2049 205012.2.1 MT Bonding Mode Selection for Multiple Switch Topology 2051------------------------------------------------------------- 2052 2053 In actual practice, the bonding mode typically employed in 2054configurations of this type is balance-rr. Historically, in this 2055network configuration, the usual caveats about out of order packet 2056delivery are mitigated by the use of network adapters that do not do 2057any kind of packet coalescing (via the use of NAPI, or because the 2058device itself does not generate interrupts until some number of 2059packets has arrived). When employed in this fashion, the balance-rr 2060mode allows individual connections between two hosts to effectively 2061utilize greater than one interface's bandwidth. 2062 206312.2.2 MT Link Monitoring for Multiple Switch Topology 2064------------------------------------------------------ 2065 2066 Again, in actual practice, the MII monitor is most often used 2067in this configuration, as performance is given preference over 2068availability. The ARP monitor will function in this topology, but its 2069advantages over the MII monitor are mitigated by the volume of probes 2070needed as the number of systems involved grows (remember that each 2071host in the network is configured with bonding). 2072 207313. Switch Behavior Issues 2074========================== 2075 207613.1 Link Establishment and Failover Delays 2077------------------------------------------- 2078 2079 Some switches exhibit undesirable behavior with regard to the 2080timing of link up and down reporting by the switch. 2081 2082 First, when a link comes up, some switches may indicate that 2083the link is up (carrier available), but not pass traffic over the 2084interface for some period of time. This delay is typically due to 2085some type of autonegotiation or routing protocol, but may also occur 2086during switch initialization (e.g., during recovery after a switch 2087failure). If you find this to be a problem, specify an appropriate 2088value to the updelay bonding module option to delay the use of the 2089relevant interface(s). 2090 2091 Second, some switches may "bounce" the link state one or more 2092times while a link is changing state. This occurs most commonly while 2093the switch is initializing. Again, an appropriate updelay value may 2094help. 2095 2096 Note that when a bonding interface has no active links, the 2097driver will immediately reuse the first link that goes up, even if the 2098updelay parameter has been specified (the updelay is ignored in this 2099case). If there are slave interfaces waiting for the updelay timeout 2100to expire, the interface that first went into that state will be 2101immediately reused. This reduces down time of the network if the 2102value of updelay has been overestimated, and since this occurs only in 2103cases with no connectivity, there is no additional penalty for 2104ignoring the updelay. 2105 2106 In addition to the concerns about switch timings, if your 2107switches take a long time to go into backup mode, it may be desirable 2108to not activate a backup interface immediately after a link goes down. 2109Failover may be delayed via the downdelay bonding module option. 2110 211113.2 Duplicated Incoming Packets 2112-------------------------------- 2113 2114 NOTE: Starting with version 3.0.2, the bonding driver has logic to 2115suppress duplicate packets, which should largely eliminate this problem. 2116The following description is kept for reference. 2117 2118 It is not uncommon to observe a short burst of duplicated 2119traffic when the bonding device is first used, or after it has been 2120idle for some period of time. This is most easily observed by issuing 2121a "ping" to some other host on the network, and noticing that the 2122output from ping flags duplicates (typically one per slave). 2123 2124 For example, on a bond in active-backup mode with five slaves 2125all connected to one switch, the output may appear as follows: 2126 2127# ping -n 10.0.4.2 2128PING 10.0.4.2 (10.0.4.2) from 10.0.3.10 : 56(84) bytes of data. 212964 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.7 ms 213064 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!) 213164 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!) 213264 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!) 213364 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!) 213464 bytes from 10.0.4.2: icmp_seq=2 ttl=64 time=0.216 ms 213564 bytes from 10.0.4.2: icmp_seq=3 ttl=64 time=0.267 ms 213664 bytes from 10.0.4.2: icmp_seq=4 ttl=64 time=0.222 ms 2137 2138 This is not due to an error in the bonding driver, rather, it 2139is a side effect of how many switches update their MAC forwarding 2140tables. Initially, the switch does not associate the MAC address in 2141the packet with a particular switch port, and so it may send the 2142traffic to all ports until its MAC forwarding table is updated. Since 2143the interfaces attached to the bond may occupy multiple ports on a 2144single switch, when the switch (temporarily) floods the traffic to all 2145ports, the bond device receives multiple copies of the same packet 2146(one per slave device). 2147 2148 The duplicated packet behavior is switch dependent, some 2149switches exhibit this, and some do not. On switches that display this 2150behavior, it can be induced by clearing the MAC forwarding table (on 2151most Cisco switches, the privileged command "clear mac address-table 2152dynamic" will accomplish this). 2153 215414. Hardware Specific Considerations 2155==================================== 2156 2157 This section contains additional information for configuring 2158bonding on specific hardware platforms, or for interfacing bonding 2159with particular switches or other devices. 2160 216114.1 IBM BladeCenter 2162-------------------- 2163 2164 This applies to the JS20 and similar systems. 2165 2166 On the JS20 blades, the bonding driver supports only 2167balance-rr, active-backup, balance-tlb and balance-alb modes. This is 2168largely due to the network topology inside the BladeCenter, detailed 2169below. 2170 2171JS20 network adapter information 2172-------------------------------- 2173 2174 All JS20s come with two Broadcom Gigabit Ethernet ports 2175integrated on the planar (that's "motherboard" in IBM-speak). In the 2176BladeCenter chassis, the eth0 port of all JS20 blades is hard wired to 2177I/O Module #1; similarly, all eth1 ports are wired to I/O Module #2. 2178An add-on Broadcom daughter card can be installed on a JS20 to provide 2179two more Gigabit Ethernet ports. These ports, eth2 and eth3, are 2180wired to I/O Modules 3 and 4, respectively. 2181 2182 Each I/O Module may contain either a switch or a passthrough 2183module (which allows ports to be directly connected to an external 2184switch). Some bonding modes require a specific BladeCenter internal 2185network topology in order to function; these are detailed below. 2186 2187 Additional BladeCenter-specific networking information can be 2188found in two IBM Redbooks (www.ibm.com/redbooks): 2189 2190"IBM eServer BladeCenter Networking Options" 2191"IBM eServer BladeCenter Layer 2-7 Network Switching" 2192 2193BladeCenter networking configuration 2194------------------------------------ 2195 2196 Because a BladeCenter can be configured in a very large number 2197of ways, this discussion will be confined to describing basic 2198configurations. 2199 2200 Normally, Ethernet Switch Modules (ESMs) are used in I/O 2201modules 1 and 2. In this configuration, the eth0 and eth1 ports of a 2202JS20 will be connected to different internal switches (in the 2203respective I/O modules). 2204 2205 A passthrough module (OPM or CPM, optical or copper, 2206passthrough module) connects the I/O module directly to an external 2207switch. By using PMs in I/O module #1 and #2, the eth0 and eth1 2208interfaces of a JS20 can be redirected to the outside world and 2209connected to a common external switch. 2210 2211 Depending upon the mix of ESMs and PMs, the network will 2212appear to bonding as either a single switch topology (all PMs) or as a 2213multiple switch topology (one or more ESMs, zero or more PMs). It is 2214also possible to connect ESMs together, resulting in a configuration 2215much like the example in "High Availability in a Multiple Switch 2216Topology," above. 2217 2218Requirements for specific modes 2219------------------------------- 2220 2221 The balance-rr mode requires the use of passthrough modules 2222for devices in the bond, all connected to an common external switch. 2223That switch must be configured for "etherchannel" or "trunking" on the 2224appropriate ports, as is usual for balance-rr. 2225 2226 The balance-alb and balance-tlb modes will function with 2227either switch modules or passthrough modules (or a mix). The only 2228specific requirement for these modes is that all network interfaces 2229must be able to reach all destinations for traffic sent over the 2230bonding device (i.e., the network must converge at some point outside 2231the BladeCenter). 2232 2233 The active-backup mode has no additional requirements. 2234 2235Link monitoring issues 2236---------------------- 2237 2238 When an Ethernet Switch Module is in place, only the ARP 2239monitor will reliably detect link loss to an external switch. This is 2240nothing unusual, but examination of the BladeCenter cabinet would 2241suggest that the "external" network ports are the ethernet ports for 2242the system, when it fact there is a switch between these "external" 2243ports and the devices on the JS20 system itself. The MII monitor is 2244only able to detect link failures between the ESM and the JS20 system. 2245 2246 When a passthrough module is in place, the MII monitor does 2247detect failures to the "external" port, which is then directly 2248connected to the JS20 system. 2249 2250Other concerns 2251-------------- 2252 2253 The Serial Over LAN (SoL) link is established over the primary 2254ethernet (eth0) only, therefore, any loss of link to eth0 will result 2255in losing your SoL connection. It will not fail over with other 2256network traffic, as the SoL system is beyond the control of the 2257bonding driver. 2258 2259 It may be desirable to disable spanning tree on the switch 2260(either the internal Ethernet Switch Module, or an external switch) to 2261avoid fail-over delay issues when using bonding. 2262 2263 226415. Frequently Asked Questions 2265============================== 2266 22671. Is it SMP safe? 2268 2269 Yes. The old 2.0.xx channel bonding patch was not SMP safe. 2270The new driver was designed to be SMP safe from the start. 2271 22722. What type of cards will work with it? 2273 2274 Any Ethernet type cards (you can even mix cards - a Intel 2275EtherExpress PRO/100 and a 3com 3c905b, for example). For most modes, 2276devices need not be of the same speed. 2277 2278 Starting with version 3.2.1, bonding also supports Infiniband 2279slaves in active-backup mode. 2280 22813. How many bonding devices can I have? 2282 2283 There is no limit. 2284 22854. How many slaves can a bonding device have? 2286 2287 This is limited only by the number of network interfaces Linux 2288supports and/or the number of network cards you can place in your 2289system. 2290 22915. What happens when a slave link dies? 2292 2293 If link monitoring is enabled, then the failing device will be 2294disabled. The active-backup mode will fail over to a backup link, and 2295other modes will ignore the failed link. The link will continue to be 2296monitored, and should it recover, it will rejoin the bond (in whatever 2297manner is appropriate for the mode). See the sections on High 2298Availability and the documentation for each mode for additional 2299information. 2300 2301 Link monitoring can be enabled via either the miimon or 2302arp_interval parameters (described in the module parameters section, 2303above). In general, miimon monitors the carrier state as sensed by 2304the underlying network device, and the arp monitor (arp_interval) 2305monitors connectivity to another host on the local network. 2306 2307 If no link monitoring is configured, the bonding driver will 2308be unable to detect link failures, and will assume that all links are 2309always available. This will likely result in lost packets, and a 2310resulting degradation of performance. The precise performance loss 2311depends upon the bonding mode and network configuration. 2312 23136. Can bonding be used for High Availability? 2314 2315 Yes. See the section on High Availability for details. 2316 23177. Which switches/systems does it work with? 2318 2319 The full answer to this depends upon the desired mode. 2320 2321 In the basic balance modes (balance-rr and balance-xor), it 2322works with any system that supports etherchannel (also called 2323trunking). Most managed switches currently available have such 2324support, and many unmanaged switches as well. 2325 2326 The advanced balance modes (balance-tlb and balance-alb) do 2327not have special switch requirements, but do need device drivers that 2328support specific features (described in the appropriate section under 2329module parameters, above). 2330 2331 In 802.3ad mode, it works with systems that support IEEE 2332802.3ad Dynamic Link Aggregation. Most managed and many unmanaged 2333switches currently available support 802.3ad. 2334 2335 The active-backup mode should work with any Layer-II switch. 2336 23378. Where does a bonding device get its MAC address from? 2338 2339 When using slave devices that have fixed MAC addresses, or when 2340the fail_over_mac option is enabled, the bonding device's MAC address is 2341the MAC address of the active slave. 2342 2343 For other configurations, if not explicitly configured (with 2344ifconfig or ip link), the MAC address of the bonding device is taken from 2345its first slave device. This MAC address is then passed to all following 2346slaves and remains persistent (even if the first slave is removed) until 2347the bonding device is brought down or reconfigured. 2348 2349 If you wish to change the MAC address, you can set it with 2350ifconfig or ip link: 2351 2352# ifconfig bond0 hw ether 00:11:22:33:44:55 2353 2354# ip link set bond0 address 66:77:88:99:aa:bb 2355 2356 The MAC address can be also changed by bringing down/up the 2357device and then changing its slaves (or their order): 2358 2359# ifconfig bond0 down ; modprobe -r bonding 2360# ifconfig bond0 .... up 2361# ifenslave bond0 eth... 2362 2363 This method will automatically take the address from the next 2364slave that is added. 2365 2366 To restore your slaves' MAC addresses, you need to detach them 2367from the bond (`ifenslave -d bond0 eth0'). The bonding driver will 2368then restore the MAC addresses that the slaves had before they were 2369enslaved. 2370 237116. Resources and Links 2372======================= 2373 2374The latest version of the bonding driver can be found in the latest 2375version of the linux kernel, found on http://kernel.org 2376 2377The latest version of this document can be found in either the latest 2378kernel source (named Documentation/networking/bonding.txt), or on the 2379bonding sourceforge site: 2380 2381http://www.sourceforge.net/projects/bonding 2382 2383Discussions regarding the bonding driver take place primarily on the 2384bonding-devel mailing list, hosted at sourceforge.net. If you have 2385questions or problems, post them to the list. The list address is: 2386 2387bonding-devel@lists.sourceforge.net 2388 2389 The administrative interface (to subscribe or unsubscribe) can 2390be found at: 2391 2392https://lists.sourceforge.net/lists/listinfo/bonding-devel 2393 2394Donald Becker's Ethernet Drivers and diag programs may be found at : 2395 - http://www.scyld.com/network/ 2396 2397You will also find a lot of information regarding Ethernet, NWay, MII, 2398etc. at www.scyld.com. 2399 2400-- END -- 2401