Swarm Network Bonding Modes
Network port bonding modes supported under Swarm (as supported by the Linux kernel) are:
active-backup (bonding mode 1)
balance-alb (bonding mode 6)
802.3ad (bonding mode 4)
Bonding mode 6 (balance-alb) is supported when using a single peer switch. If the requirement calls for use of multiple switch chassis to provide switch layer redundancy, configure Swarm to use bonding mode 1 (active-backup). You may also choose bonding mode 4 (802.3ad) with further planning and testing. Considerations for that are outlined below.
Bonding mode 1 (active-backup) is advised for “out of the box” multi-switch and MLAG configurations, whereas bonding mode 4 (802.3ad) needs additional configuration on the switch side to function. Since failover and traffic balancing with MLAG is proprietary to switch vendors, it is necessary to review switch capability to determine the appropriate bonding mode for MLAG (i.e., bonding mode 1 or 4 i.e. active-backup or 802.3ad).
Use of Multi-port NICs with Swarm
Swarm bonds the NIC ports it detects and uses a single IP address for the bond definition. Note that multiport network cards (two or more ports per card) aren’t considered fully redundant when used in Swarm storage hosts. Multiport NICs experience common failure modes which can disconnect a Swarm host completely. A true 'active-active' design includes the use of separate NICs in the storage hosts to meet that requirement.
PXE Boot in MLAG Configuration
PXE passthrough behavior is very important in either an L2 or L3 MLAG configuration. Configuring nodes for network (PXE) boot when 802.3ad and MLAG are in place can prove difficult to use for such network configurations. Vendor implementation of PXE passthrough for MLAG can behave inconsistently, therefore active-backup bonding mode is strongly advised for use in this scenario.