[c-nsp] Fwd: Re: QinQ

[sthaug at nethelp.no]

> Is Spanning tree (specifcally MSTP) work over QinQ links - i.e. a topology 
> like below:
> 
> i.e. STP for the Provider backbone (not for the Customer 802.1q tags).
> 
> i.e. the following is not protected by STP?? (MSTP in my case):
> 
> SW   - w 802.1q VLAN (2950/2400ME)
> CSW - Core Switch with QinQ trunks (3550 w EMI / 3560)
> 
>                   /---------------------\
> SW----CSW1|                     | CSW2----SW
>                   \---------------------/

I see no reason why STP for the provider backbone shouldn't work for
L2 transport via a Martini tunnel. Remember, a Martini tunnel (or for
instance L2TPv3) is ideally just a pipe, and there is no reason for the
routers at each end to do MAC learning, special treatment of STP BPDUs
etc.

I haven't tested this for Martini tunnels between Cisco routers - it
works for other vendors in our backbone.

Steinar Haug, Nethelp consulting, sthaug at nethelp.no