Port Trunks

mattesong · ‎08-26-2008

Can someone explain to me what 'vlan dot1q tag native' does? and what the native vlan is and how it relates to trunking? i ran into a problem earlier today and was able to fix it by using that command.... not sure if that is the right way or what i really did, looking for some explanations. thank you, greatly appreciated

yandy_ramirez · ‎08-26-2008

well, by default the native vlan on a trunk default (vlan 1) is not tagged with a dot1q tag. That command tells the switch to tag the native vlan on whatever trunk port it is configured.. so all vlans will carry a dot1q tag. dont know that situation but you might have had a native vlan mismatch on the trunk and tagging it resolved it on one of the sides, but i doubt that was the correct solution.

Jon Marshall · ‎08-26-2008

On an 802.1q trunk all vlans are tagged with a vlan ID except for the native vlan which is sent untagged. The native vlan can be any vlan you want although as Yandy says it is by default vlan 1.

The reason for a native vlan is to provide backwards compatability with older switches that do not understand vlan tagging. You can choose to tag the native vlan if this isn't needed.

Jon