Mobility Express mac flapping

Cause Analysis

Mobility Express environment allows redundancy, If the Master AP fails, another AP(MOBILITY EXPRESS CAPABLE image installed) will become the Master AP. VRRP plays an important role in the Failover process of ME, VRRP is used to detect a failure of Master AP and to elect a new Master. The VRID of Cisco Mobility Express was fixed as 01, so the default VRRP MAC is 0000.5e00.0101. If the same VRID is used in Mobility Express environment, it will cause VRRP MAC conflict. The following error message may appear at this time(on the switch).

%SW_MATM-4-MACFLAP_NOTIF: Host 0000.5e00.0101 in vlan xxx is flapping between port Gi0/x and port Gi0/x

Solution

Given this situation, for versions above 8.8 we can configure the VRID with the following command.

config mob-exp vrid new_vrid

If you are experiencing mac flapping in the Mobility Express environment, the following commands may help you troubleshoot.

# WLC
show mob-exp vrrp vrid
show mob-exp vrrp mac
# AP
show flexconnect mobexp vrrp events
show flexconnect mobexp vrrp stats
show flexconnect mobexp vrrp status

Updated on September 4, 2020: The commands changed after 8.10 are as follows.

# AP
show vrrp events
show vrrp statistics
show vrrp status

References

Mobility Express uses MAC 00-00-5E-00-01-VRID where VRID is 1 so if there are other instances of VRRP running in the environment, use VRID other than 1 for those instances.

Master AP Failover and Electing a New Master

Beginning Cisco Wireless Release 8.8, when a VRRP MAC conflict is detected, you can change the VRID on the master AP.

Configuring VRID

To configure a new VRID. The range for new_vrid
 is 1 to 255 where the default is 1.

VRRP Commands