Multi-active handling procedure
The multi-active handling procedure includes detection, collision handling, and failure recovery.
Detection
MAD identifies each IRF fabric with a domain ID and an active ID (the member ID of the master). If multiple active IDs are detected in a domain, MAD determines that an IRF collision or split has occurred.
For more information about the MAD mechanisms and their application scenarios, see "MAD mechanisms."
Collision handling
When MAD detects a multi-active collision, it sets all IRF fabrics except one to the Recovery state. The fabric that is not placed in Recovery state can continue to forward traffic. The Recovery-state IRF fabrics are inactive and cannot forward traffic.
LACP MAD uses the following process to handle a multi-active collision:
Compares the number of members in each fabric.
Sets all fabrics to the Recovery state except the one that has the most members.
Compares the member IDs of the masters if all IRF fabrics have the same number of members.
Sets all fabrics to the Recovery state except the one that has the lowest numbered master.
Shuts down all service interfaces in the Recovery-state fabrics except for the following service interfaces:
IRF physical interfaces.
Service interfaces specified by using the mad exclude interface command.
In contrast, BFD MAD, ARP MAD, and ND MAD do not compare the number of members in fabrics. These MAD mechanisms use the following process to hand a multi-active collision:
Compare the member IDs of the masters in the IRF fabrics.
Set all fabrics to the Recovery state except the one that has the lowest numbered master.
Take the same action on the service interfaces in Recovery-state fabrics as LACP MAD.
Failure recovery
To merge two split IRF fabrics, first repair the failed IRF link and remove the IRF link failure.
If the IRF fabric in Recovery state fails before the failure is recovered, repair the failed IRF fabric and the failed IRF link.
If the active IRF fabric fails before the failure is recovered, enable the inactive IRF fabric to take over the active IRF fabric. Then, recover the MAD failure.