IPv6 BGP Behavior During Unified ISSU

You can perform unified in-service software upgrade (ISSU) without terminating the BGP IPv6 peer sessions and with less impact on network outages. When the unified ISSU operation is initiated using the issu start command, the unified ISSU operation will trigger a series of signals. The BGP component handles these signals and validates the following optional criteria for BGP IPv6 address families:

If any of these criteria are not met, the unified ISSU infrastructure will generate appropriate warning messages before starting unified ISSU. If the criteria are met, BGP will send a keepalive message for each peer and report back to the unified ISSU infrastructure.

During the interface controller restart, switch route processor (SRP) switchover, and forwarding controller restart phases of the unified ISSU operation, BGP will not be able to communicate with its IPv6 peers and the peers may terminate the BGP sessions. To avoid the termination, BGP sends a keepalive message before the restart and switchover phases, independent of the interval since the last message sent by BGP.

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