How the
Multi-Chassis
role works
The switch performs the STP operation on the switch that has the
Multi-Chassis
role set to active. The switch with the role set to standby relays the information to the switch with the active role for STP tasks.
The primary VSX switch has the
Multi-Chassis
role set to active by default, just as the secondary VSX switch has the
Multi-Chassis
role set to standby by default. The
Multi-Chassis
role on the secondary VSX switch changes from standby to active if the primary VSX switch goes down.
The
show spanning-tree vlan
<VLAN-ID> detail
command provides information about the value of the
Multi-Chassis
role. In the following example, the primary switch has the
Multi-Chassis
role set to active, and the secondary switch has the
Multi-Chassis
role set to standby.
Example of the
Multi-Chassis
role with the active value:
VSX-Primary# show spanning-tree vlan 2 detail VLAN2 Spanning tree status : Enabled Protocol: RPVST Root ID Priority : 32768 MAC-Address: 38:21:c7:66:24:00 This bridge is the root Hello time(in seconds):2 Max Age(in seconds):20 Forward Delay(in seconds):15 Bridge ID Priority : 32768 MAC-Address: 38:21:c7:66:24:00 Hello time(in seconds):2 Max Age(in seconds):20 Forward Delay(in seconds):15 Port Role State Cost Priority Type ------------ -------------- ------------ ------------ ---------- ---------- 1/3/1 Designated Forwarding 1 128 point_to_point lag2 Designated Forwarding 20000 64 point_to_point Topology change flag : True Number of topology changes : 3 Last topology change occurred : 47 seconds ago Port 1/3/1 Designated root has priority :32768 Address: 38:21:c7:66:24:00 Designated bridge has priority :32768 Address: 38:21:c7:66:24:00 Designated port : 1153 Number of transitions to forwarding state : 1 Bpdus sent 28, received 28 TCN_Tx: 2, TCN_Rx: 0 Port lag2 Designated root has priority :32768 Address: 38:21:c7:66:24:00 Designated bridge has priority :32768 Address: 38:21:c7:66:24:00 Designated port : 770 Multi-Chassis role :active Number of transitions to forwarding state : 1 Bpdus sent 28, received 3 TCN_Tx: 2, TCN_Rx: 2 VSX-Secondary# show spanning-tree vlan 2 detail VLAN2 Spanning tree status : Enabled Protocol: RPVST Root ID Priority : 32768 MAC-Address: 38:21:c7:66:24:00 This bridge is the root Hello time(in seconds):2 Max Age(in seconds):20 Forward Delay(in seconds):15 Bridge ID Priority : 32768 MAC-Address: 38:21:c7:66:24:00 Hello time(in seconds):2 Max Age(in seconds):20 Forward Delay(in seconds):15 Port Role State Cost Priority Type ------------ -------------- ------------ ------------ ---------- ---------- 1/3/1 Designated Forwarding 1 128 point_to_point lag2 Designated Forwarding 20000 64 point_to_point Topology change flag : False Number of topology changes : 2 Last topology change occurred : 35 seconds ago Port 1/3/1 Designated root has priority :32768 Address: 38:21:c7:66:24:00 Designated bridge has priority :32768 Address: 38:21:c7:66:24:00 Designated port : 129 Number of transitions to forwarding state : 2 Bpdus sent 24, received 22 TCN_Tx: 1, TCN_Rx: 2 Port lag2 Designated root has priority :-32768 Address: 38:21:c7:66:24:00 Designated bridge has priority :-32768 Address: 38:21:c7:66:24:00 Designated port :770 Multi-Chassis role :standby Number of transitions to forwarding state : 3 Bpdus sent 0, received 0 TCN_Tx: 0, TCN_Rx: 0