Troubleshooting Switched Connections
607
Some of these commands have been covered in previous chapters and will
not be repeated here. The commands that have not been discussed are
covered below. The debug commands provide debug information with
respect to VLAN packets and the spanning tree protocol.
show vlans
This command is executed from the router and it displays the details about the
VLANs configured on the router. The detail includes the VLAN name, the inter-
face, and the IP address used. It also includes the VLAN protocol (encapsulation)
and interface protocol such as IP or IPX. Here is a sample:
Router_A#show vlans
Virtual LAN ID: 1 (Inter Switch Link Encapsulation)
vLAN Trunk Interface: FastEthernet1/0.1
Protocols Configured: Address: Received:
Transmitted:
IP 172.16.1.1 4236441842
854332923
Virtual LAN ID: 2 (Inter Switch Link Encapsulation)
vLAN Trunk Interface: FastEthernet1/0.2
Protocols Configured: Address: Received:
Transmitted:
IP 172.16.2.1 3002644583
2325942305
Router_A#
show spanning-tree
For IOS revisions prior to 12.0T, this command was known as show span (not
to be confused with the similar command for switches). In the 12.0T IOS
release the command was changed to show spanning-tree. This command
displays spanning tree information for the router.
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