[c-nsp] q-in-q breaking multicast?

[Jon Lewis]

We have a setup where a pair of our 6500 switches each connect via FE to a 
telco's ME3400 switch, and the telco provides ethernet connectivity from 
customers back to us using q-in-q.  We deploy small vlan capable switches 
(i.e. 2912xl) as CPE and each is configured to use a different vlan which 
the telco tunnels though their network and passes back to us.

I just tried setting up vrrp on the 6500s for one of these customer vlans 
and found that neither 6500 would see the other's vrrp multicast packets, 
and so each thought it was the only router and became the active router. 
Is this a known issue when connecting switches to ports configured with 
"switchport mode dot1q-tunnel"?

I'm guessing we can fix this by putting a small L2 switch between the 
teclo's ME3400 and our 6500s, but I'm wondering if there's a way to fix 
this without adding more gear and cabling?

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  Jon Lewis                   |  I route
  Senior Network Engineer     |  therefore you are
  Atlantic Net                |
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