[c-nsp] Why it won't route vlan 1 ?

[Jerome Covini]

Jared Mauch wrote:
> On Tue, May 15, 2007 at 05:52:21PM +0200, jcovini at free.fr wrote:
>   
>> Running 12.2.18SXF8 on sup720-3b/6506
>>
>> Router(config)#int gi1/1
>> Router(config-if)#no switchport
>> Router(config-if)#int gi1/1.1
>> Router(config-subif)#encapsulation isl 1
>> Command rejected: VLAN 1 cannot be allocated because it is a default VLAN
>> Router(config-subif)#encapsulation dot1Q 1 native
>> Command rejected: VLAN 1 cannot be allocated because it is a default VLAN
>>
>> However this was working like a charm on older IOS versions, or onto other
>> platforms, so is it a platform limitation ? Is it due to 12.2.18SXF8 ? Should I
>> consider a change towards SXD train ? I am heritating of this design and need to
>> route all my .1 subinterfaces, without renumbering them if possible.
>>     
>
> 	There is only one 'vlan1'
>
> 	if you have vlan1 on more than one interface (eg: gig1/1 and gig1/2)
> they are actually the same vlan.  This device is a switch, not an
> independent router.
> 	You should be able to 'no shut' the vlan1 interface and use that
> instead and leave the port as a trunk.  vlan1 has been generally 
> 'pseudo-reserved' on cisco for as long as I can remember.  I suspect
> that it was working some other way was some odd artifact of the code that
> they've since closed to prevent unexpected operation.
>
> 	- Jared
>
>   

For info, the platform onto which it was working was a totally different 
one i.e. Cisco 8540CSR with 2port GE modules.
This was accepting to have multiple vlan 1 routed subinterfaces, as well 
as multiple vlan x routed subinterfaces . Probably the odd code artefact 
you are referring to !