Common Inter-VLAN Issues and Solutions

First, check the physical layer to resolve any issues where a cable might be connected to the wrong port

Issue Type	How to Fix	How to Verify
Missing VLANs	Create the VLAN if it does not exist. Ensure host port is assigned to the correct VLAN.	show vlan [brief] show interfaces switchport ping
Switch Trunk Port Issues	Ensure trunks are configured correctly. Ensure port is a trunk port and enabled.	show interface trunk show running-config
Switch Access Port Issues	Assign correct VLAN to access port. Ensure port is an access port and enabled. Host is incorrectly configured in the wrong subnet.	show interfaces switchport show running-config interface ipconfig
Router Configuration Issues	Router subinterface IPv4 address is incorrectly configured. Router subinterface is assigned to the VLAN ID.	show ip interface brief show interfaces