The common system MAC address

The common system MAC address is used for preventing traffic disruptions when the primary switch is restored after the secondary switch. A primary switch might be restored after the secondary switch in scenarios, such as:

• A primary switch hardware replacement.

• A power outage with the primary switch restored after the secondary switch is restored.

When the primary switch is restored after the secondary switch, a traffic disruption might occur when the ISL starts to sync because the MAC system address changes from the secondary switch to the primary switch for the LACP. To avoid the traffic disruption, set the common system MAC address by entering the system-mac <MAC-ADDR> command. This command creates a common system MAC address between the two VSX switches. This common system MAC address prevents a traffic disruption when the secondary switch comes up before the primary switch. If the common system MAC access is enabled, the secondary switch uses the common system MAC address instead of its own system MAC address, which prevents a traffic loss.

The system MAC address also maintains the same MSTP bridge ID across VSX switches, which act as a single switch.