From: Brant I. Stevens (branto@branto.com)
Date: Sun May 08 2005 - 18:33:54 GMT-3
I was under the impression that true 802.1q-compliant systems do not tag the
native VLAN whatsoever, but Cisco provided that knob for vendors that did
not exactly comply with the spec (or was it that they themselves didn't
adhere religiously to the spec on some of their gear? Or is it nostalgia for
ISL?)
Thanks for the clarification regarding the use of dynamic trunking mode.
On 5/7/05 7:57 PM, "James Ventre" <messageboard@ventrefamily.com> wrote:
> That depends on your trunking configuration.
>
> Set you trunk to desirable, and you can have a native vlan if you're
> trunking, and a different vlan if it's not trunking. The native VLAN on
> a trunk is just the VLAN that is untagged. If you hardcode the trunk to
> "on" then your explaination applies.
>
> Here is an example:
>
> interface FastEthernet0/2
> switchport access vlan 5
> switchport mode dynamic desirable
> !
>
> If you're trunking, the native VLAN is 1. If you're not trunking, the
> access VLAN is 5.
>
>
> You don't have to have an "untagged" native vlan on 802.1Q trunks - this
> command makes all vlans tagged:
> switch(config)#vlan dot1q tag native
>
>
>
> James
>
>
>
>
>
>
>
>
> Brant I. Stevens wrote:
>
>> The native VLAN of a trunk link is the port assignment of a given
>> port/interface should it not be trunking. With 802.1q, frames originating
>> from the native vlan are not tagged with a VLAN assignment as they cross the
>> trunk link; you don't really have a choice to not use a native VLAN. If you
>> do not explicitly set the native VLAN of a trunk, it is left in the default
>> VLAN (1).
>
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