Due to the way the IKEv2 protocol is designed the FGCP cannot use exactly the same solution that is used for synchronizing IKEv1 SAs, though it is similar.

For IKEv2, like IKEv1, the FGCP synchronizes IKE and ISAKMP SAs from the primary unit to the subordinate units. However, for IKEv2 the FGCP cannot actually use this IKE SA to send/receive IKE traffic because IKEv2 includes a sequence number in every IKE message and thus it would require synchronizing every message to the subordinate units to keep the sequence numbers on the subordinate units up to date.

Instead, the FGCP synchronizes IKEv2 Message IDs. This Message ID Sync allows IKEv2 to re-negotiate send and receive message ID counters after a failover. By doing this, the established IKE SA can remain up, instead of re-negotiating.

The diagnose vpn ike stats command shows statistics for the number of HA messages sent/received for IKEv2. The output of this command includes a number of fields prefixed with ha that contain high availably related-data. For example: