Verifying Trunk Links

Verifying Trunk Links
On the 4000 series, you can verify your trunk ports using the show trunk command. If you
have more than one port trunking and want to see statistics on only one trunk port, you can use
the show trunk port_number command:
Terry_4000> (enable) show trunk 2/12
Port Mode Encapsulation Status Native vlan
-------- ----------- ------------- ------------ -----------
2/12 on isl trunking 1
Port Vlans allowed on trunk
-------- ------------------------------------------------------
2/12 1-4
Port Vlans allowed and active in management domain
-------- ------------------------------------------------------
2/12 1
Port Vlans in spanning tree forwarding state and not pruned
-------- ------------------------------------------------------
2/12 1
Terry_4000> (enable)
The 2950/3550 series of Catalyst switches continue to do it differently than the 4000.
To view the trunk status of a port on one of these switches, the command show interface
interface_id switchport needs to be used:
Terry_2950#show interface fa0/10 switchport
Name: Fa0/10
Switchport: Enabled
Administrative Mode: trunk
Operational Mode: down
Using VLAN Trunk Protocol (VTP) 465
Administrative Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Operational private-vlan: none
Trunking VLANs Enabled: 1,11,13,14,16-1005
Pruning VLANs Enabled: 2-1001
Protected: false
Voice VLAN: none (Inactive)
Appliance trust: none
Terry_2950#
A VLAN that is enabled on the switch is one that the switch has learned exists in the switch
fabric of the LAN. Somewhere out there, a device needs that particular VLAN, or it might be
configured for future use. An active VLAN is a VLAN in which one or more ports on this switch
are members.