[c-nsp] VLAN internal usage

Peter Rathlev peter at rathlev.dk
Tue Dec 2 15:19:12 EST 2008

On Tue, 2008-12-02 at 14:56 -0300, Leonardo Gama Souza wrote:
> I am wondering why I can see some VLANs configured on L3 interfaces in
> the internal VLAN usage.
> Wasn't it supposed to show up only internal VLANs allocated from the
> range 1006-4094? 
> For example:
> 7609#show vlan inter usage
> VLAN Usage
> ---- --------------------
> 20    GigabitEthernet4/1.20
> 21    GigabitEthernet4/1.21     <<<<<<< new subinterface accounted as

Subinterfaces use "internal VLANs" and are not switched like other
VLANs. If you were using the VLANs as regular switchport VLANs on a
trunk, they wouldn't consume "internal VLANs", but subinterfaces do.

This also means that this VLAN is reserved for exactly that port, and
that you can't use the same VLAN on another physical port. (Cf. the "no
local vlan significance" discussion recently on this list.)


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