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Implementing Cisco Networking Solutions by Harpreet Singh

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Troubleshooting layer 2 issues

A switched network at the access could have multiple VLANs. The show vlan brief command shows the VLAN database that shows all VLANs configured on the device. This command also shows the VLAN to port mappings. The command also shows the MTU for each VLAN. A trimmed output of the command is as shown in the following image:

Figure 13: Finding port to VLAN mappings

A VLAN may sometimes need to be tracked all the way up to the first layer 3 device. This can be done using the show interfaces trunk command. This will show the trunk ports and VLANs configured on the trunk ports. A sample output is as shown in the following ...

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