[c-nsp] Replacing proper planning with dirty hacks (VLAN extension over GRE & L2TP)

[Brad Henshaw]

Phil,

Thanks for the input. Further responses...

> I think the original poster had a VPLS-like scenario in mind, where  
> the headend is acting like a virtual switch of sorts.
> You aren't going to find  VPLS support on any of the lower end
> models of routers.   If you just tunnel everything through to a
> switch outside the routers, then you would be fine.

That was the type of general topology I was thinking about, yes.
If we need a switch and the headend to deal with L2 switching
between the tunnels then it probably doesn't matter too much
in the grand scheme of things.

> Alcatel's 7750/7450 has a feature called spoke-sdp which will use GRE  
> tunnels (or native MPLS) to create VPLS instances between
> a hub (7750) and spokes (7450), that works very well.   I think Cisco  
> is working on similar features since they just came out with AToGRE with
> SRB on the 7600, but I wouldn't expect that to be supported on any  
> lower end platforms.

Interesting. I shall read more.

> If it were me I'd leave at L3

As would I, and that may be a position we end up in. Basically leaving
it at L3 doesn't meet the customer's requirements for transport of
the various VLANs across the site - but they may just have to live
without it if they're not going to look at L2 radios.

> I saw something about support for VRFs for  
> multipoint VPNs I think, so you may be able to use a few multipoint  
> GRE tunnels on the headend

I found a couple of references to multipoint VPNs but only looked
briefly and couldn't find any useful implementation doco that focused
on the GRE side of it. Will quiz the local Cisco SEs regarding this
today.

> one for each service so to speak, as  
> opposed to one for every service on every router...sounds like fun  
> any way you slice it.  :)

Ah huh!

Regards,
Brad