Network bonding modes
Network port bonding modes 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 is multiple switch chassis to provide switch layer redundancy, configure Swarm to use either bonding mode 1 (active-backup) or bonding mode 4 (802.3ad).
Bonding mode 1 (active-backup) is advised for multi-chassis link aggregation whereas bonding mode 4 (802.3ad) needs additional configuration on the switch side to function. Since failover and traffic balancing with link aggregation (using multiple switch chassis) are proprietary to switch vendors, it is necessary to review switch capability to determine the appropriate bonding mode for multi-chassis link aggregation (i.e., bonding mode 1 or 4).
Swarm bonds the NICs and uses a single IP address for the bond. Multiport network cards (two or more ports per card) are necessary when considering failover for the 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
The PXE passthrough modes are important in either an L2 or L3 MLAG configuration. Getting nodes to the network boot when 802.3ad and MLAG are in place is a major pain point for such deployments. None of them behave the same way either, therefore, active-backup bonding mode is strongly advised to use.