The following example shows the output from the show spanning-tree mst command, which produces more
detailed information regarding interface state than the standard command as described above:
# show spanning-tree mst a interface GigabitEthernet0/1/2/1
GigabitEthernet0/1/2/1
Cost: 20000
link-type: point-to-point
hello-time 1
Portfast: no
BPDU Guard: no
Guard root: no
Guard topology change: no
BPDUs sent 492, received 3
MST 3:
Edge port:
Boundary : internal
Designated forwarding
Vlans mapped to MST 3: 1-2,4-2999,4000-4094
Port info port id 128.193 cost 200000
Designated root address 0050.3e66.d000 priority 8193 cost 20004
Designated bridge address 0002.172c.f400 priority 49152 port id 128.193
Timers: message expires in 0 sec, forward delay 0, forward transitions 1
Transitions to reach this state: 12
The output includes interface information about the interface which applies to all MSTIs:
• Cost
• link-type
• hello-time
• portfast (including whether BPDU guard is enabled)
• guard root
• guard topology change
• BPDUs sent, received.
It also includes information specific to each MSTI:
• Port ID, priority, cost
• BPDU information from root (bridge ID, cost, and priority)
• BPDU information being sent on this port (Bridge ID, cost, priority)
• State transitions to reach this state.
• Topology changes to reach this state.
• Flush containment status for this MSTI.
This example shows the output of show spanning-tree mst errors, which produces information about interfaces
that are configured for MSTP but where MSTP is not operational. Primarily this shows information about
interfaces which do not exist:
# show spanning-tree mst a errors
Interface Error
-------------------------------
GigabitEthernet1/2/3/4 Interface does not exist.
L2VPN and Ethernet Services Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.3.x
454
Implementing Multiple Spanning Tree Protocol
Configuring MSTP: Examples
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