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The "port is a non-802.1q port" error message is displayed on Cisco Catalyst switches that run CatOS


Core issue

The root cause of this issue is that the native VLAN can only be in a dot1q trunk. An attempt to change the native VLAN of a trunk port results in the port is a non-802.1q port error message.

Issue the show port capabilities command to determine the supported trunking encapsulations.

All releases of Catalyst OS (CatOS) software support this command for the Catalyst 4500/4000 and Catalyst 6500/6000 series switches. The Catalyst 5500/5000 series switches first introduced support for the show port capabilities command in release 4.1.


Native VLAN requires dot1q support on hardware. In other words, dot1q for trunking is a hardware-dependent factor. Most hardware supports dot1q for trunking, but some do not.

Issue the show port capabilities command to check whether a port or module supports dot1q. Also, before using dot1q for a port, check the hardware capabilities with the same command.

For more information, refer to System Requirements to Implement Trunking.