Troubleshooting VLAN ProblemsIf you're experiencing connectivity problems in a VLAN environment, you should perform the following troubleshooting steps:
Check the status of the interface with the show interfaces command. Use CDP to check connectivity.
Check the duplexing of the connection (auto negotiation is a common problem with the negotiation of the duplexing mode).
Is your router and switch configuration correct? Verify that you've configured your routing protocol and your router's interface. If you're trunking between the router and the switch, verify this configuration.
Have you set up your VLAN configuration correctly? Check to make sure that the appropriate interfaces are associated with the correct VLANs.