Re: Native VLAN on Catalyst

From: Erick B. (erickbe@xxxxxxxxx)
Date: Thu Dec 06 2001 - 02:59:39 GMT-3


   
Hi,

The Native VLAN is the VLAN that port is in if it were
an access-port (non trunk port). With 802.1Q the
native VLAN on the trunk port is not tagged, and the
rest of the VLANs are tagged.

To put a switch port in VLAN 10 native, just assign
the port to a VLAN as you normally do.

If you had:

Switch-----Router

VLANs 10 and 20 lets say. Vlan 10 is 192.168.1.x and
VLAN 20 is 172.16.1.x.

The switch port is in vlan 10 and is a trunk port.
On the router, since the native VLAN isn't tagged you
can put 192.168.1.x IP address on the physical
ethernet interface and create a sub-interface for VLAN
20 which is tagged.

Sample router config:

int fa0/0
  ip address 192.168.1.1 255.255.255.0
int fa0/0.20
  ip address 172.16.1.1 255.255.255.0
  encaps dot1q 20

In recent IOS versions, you can have a subinterface
and do 'encaps dot1q # native' as well to put the
native VLAN on the sub-interface. In older IOSs
without 'native' option you had to put it on major.

--- Neil Garcia Legada <nlegs@visto.com> wrote:
> Hi Group,
>
> Anybody had a good explanation about native VLAN and
> whats its use for ???
>
> I just had a problem wherein one router is trunked
> connected to the switch and the switch itself has an
> RSM. Both the router and RSM are routing between
> VLAN's with HSRP. When the native VLAN on the
> devices are different they lost connectivity.
>
> Appreciate any feedback.
>
>
> Thanks and regards,
> Neil
>



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