[c-nsp] vlan problem in my router

[Justin M. Streiner]

On Mon, 27 Sep 2010, Deric Kwok wrote:

> I have problem to create vlan in my router 28 serise.
>
> I can create vlan database
>
> 1/ I can't use name command as "router(vlan)# name net1"
>
> 2/ I can't config t the vlan as "(config)#vlan 10  ===> % Invalid
> input detected at '^' marker."
>
> ls my router supporting vlan?

If you are running an IOS version that supports 802.1Q VLAN tagging, you 
can create VLANs, but they behave differently on a router than on a 
switch:

For example, on a router:

interface GigabitEthernet0/0/0
  no ip address
interface GigabitEthernet0/0/0.100
  description sub-interface for VLAN 100
  encapsulation dot1q 100
  ip address 10.10.100.1 255.255.255.0
interface GigabitEthernet0/0/0.200
  description sub-interface for VLAN 200
  encapsulation dot1q 200
  ip address 10.10.200.1 255.255.255.0

You can shut down individual sub-interfaces if you need to, and as you'd 
expect, shutting down the parent interface (Gig0/0/0 in this case) will 
take down all of the sub-interfaces.

You need to pay attention to which VLAN you use as the native VLAN on 
your trunk, and match it on the router by adding the "native" statement to 
your subinterface encapsulation command.  There are other things that need 
to match up as well, such as the encapsulation type, especially if you're 
still using something other than 802.1q.  I'm not sure if ISL is even 
supported anymore.

There are other important things to consider as well, such as which device 
acts as the root bridge for the VLANs on the trunk.

There are lots of examples and documentation for configuring VLANs and 
trunks on routers on Cisco's website.

jms