Trunk port and native vlan

Unanswered Question
Aug 16th, 2007

Hi

This is just a query. If I have native vlan configured on a layer 2 switch i.e vlan 100, and then I configure a port to be a trunk port but I don't set the "switchport trunk native vlan 100" what would be the native vlan for this port?

Second question can I configure one trunk port to have a native vlan of 100 while having another port on the same layer 2 switch configured with a native vlan of 150? If this is possible how can I route between the two native vlan's?

Thanks in advance

Dan

I have this problem too.
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royalblues Thu, 08/16/2007 - 11:57

If you do not set the port with the switchport trunk native vlan 100" then it should by default have vlan 1 as native. THis vlan will be untagged on the trunk link

It is possible to set the native vlan to 100 on one trunk port and 150 on the other. When you do this the traffic for that vlan will be untagged while travelling over that trunk. If the 2 sides of a trunk port are configured for different native VLAN, then you should see errors like

*Mar 1 00:02:47.387: %SPANTREE-2-RECV_PVID_ERR: Received BPDU with inconsistent

peer vlan id 1 on FastEthernet1/1 VLAN10.

The routing between the vlans would be a normal switching (routing) between the VLans

HTH

Narayan

Jon Marshall Thu, 08/16/2007 - 12:39

Narayan

I guess it depends on how you read it but i think Dan is asking if you can have 2 trunk ports on the same switch with different native vlan as opposed to a trunk between 2 switches with native vlan configured differently on either end.

If this is what you are asking Dan then yes you can have each trunk with a different native vlan if you want although i'm not sure why you would want to do that.

Not sure what you mean about routing between the vlans. The native vlan has nothing to do with the routing as such. The vlans will be able to route between each other as long as you have L3 SVI's for both vlans.

HTH

Jon

Edison Ortiz Thu, 08/16/2007 - 16:00

>I configure a port to be a trunk port but I don't set the "switchport trunk native vlan 100" what would be the

> native vlan for this port?

It will default to Vlan1

>Second question can I configure one trunk port to have a native vlan of 100 while having another port on the

> same layer 2 switch configured with a native vlan of 150? If this is possible how can I route between the two native

> vlan's?

You will need an external router to route between these 2 Vlans on a Layer2 switch.

You can have one port connect to one router interface and the other port connect to the same router second interface (or other router) and the router should be able to route between these Vlans.

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