When you install two Management Switch Fabric Modules (MSMs) or Management Modules (MMs) in a BlackDiamond chassis or use redundancy in a SummitStack, one MSM/MM (node) assumes the role of primary and another node assumes the role of backup.
The primary node executes the switch‘s management functions, and the backup node acts in a standby role. Hitless failover transfers switch management control from the primary to the backup and maintains the state of EAPS. EAPS supports hitless failover. You do not explicitly configure hitless failover support; rather, if you have two MSMs/MMs installed in a chassis or you are operating with redundancy in a SummitStack, hitless failover is available.
Note
Not all platforms support hitless failover in the same software release. To verify if the software version you are running supports hitless failover, see the following table in Managing the Switch. For more information about protocol, platform, and MSM/MM support for hitless failover, see Understanding Hitless Failover Support.To support hitless failover, the primary node replicates all EAPS PDUs to the backup, which allows the backup to be aware of the EAPS domain state. Since both nodes receive EAPS PDUs, each node maintains equivalent EAPS states.
By knowing the state of the EAPS domain, the EAPS process running on the backup node can quickly recover after a primary node failover. Although both nodes receive EAPS PDUs, only the primary transmits EAPS PDUs to neighboring switches and actively participates in EAPS.
Note
For instructions on how to manually initiate hitless failover, see Relinquishing Primary Status.
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