[c-nsp] vlan across a routed link

[masood at nexlinx.net.pk]

what’s wrong in extending your spanning-tree domain, as long as numbers of
nodes are not too many? People are using trunk links between different
sites across the world in an enterprise environment,  and this is for what
you use a trunk link. I would prefer the usage of trunk links and routed
VLAN interfaces over EoMPLS and VPLS. (keeping in mind the throughput
issues on EoMPLS, mtu problems and overall network complexity)

Regards,
Masood


>> teklay gebremichael wrote:
>> > i work in a university which has three campuses. on each campuse,
>> > there is one cisco 6509 switch as a core switch. all other switches
>> > (L2) are in vtp client except the core switches. the campuses are
>> > connected with a routed link. so, one campuse, has 10.128.0.0/16
>> > subnet and the others have a subnet of 10.129.0.0/16 and
>> > 10.130.0.0/16. rip v2 is used on the intercampuse links to advertise
>> > individaul vlans.
>> >
>> > here is my problem.
>> >
>> > i'm asked to create a vlan with a subnet id of 192.168.1.0/24. but
>> > computers in this vlan are located in the 10.128.0.0/16 campuse and
>> > 10.130.0.0/16 campuse.the link between the 10.128.0.0/16 and
>> > 10.130.0.0/16 is not trunk it is routed with ip address. so can any
>> > body suggest me how to implement such senario which allows one vlan
>> > (in this case 192.168.1.0/24) to be visible from the two campuses?
>> > i.e to propage that specific valn across a routed link not a trunk
>> > link. thanks
>>
>> You will need to convert the link from routed to switchport. That is,
>> transform this:
>
> right, but think about the implications before doing so. You will extend
> your spanning tree domain over all the different sites, so this just
> asks for disaster to happen. And don't mention "hey, I only do this for
> a single Vlan". Once you start offering this "service", users will ask
> for it, and you end up doing this for many.
>
> Please consider technologies for this where you don't need to extend
> spanning tree. for example L2VPN (EoMPLS, VPLS), or loop-free topologies
> using VSS where you can disable STP between campuses..
>
> 	oli
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