[c-nsp] Q-in-Q over a switchport trunk

[Jeff Bacon]

<flame suit on>
I know this seems stupid. But it's what I've got to work with.


I have several metro-e point-to-points from a major provider. Their CPE
is a ME3400-class, which is connected to my cat6504 via a gig SMF. The
connection is configured as a dot1q trunk, with each of the P-T-Ps
coming in to me on different VLANs. 

My hardware: sup720-3B, X6816A/DFC3B, 12.2(18)SXF8 (moving to 33SXH4). 

Right now, the configuration is straightforward: 

---------------------------

interface GigabitEthernet2/1
 switchport
 switchport trunk encapsulation dot1q
 switchport trunk allowed vlan 3000-3100
 switchport mode trunk
 switchport vlan mapping enable
 switchport vlan mapping 3467 3004
 switchport vlan mapping 3610 3003
 switchport vlan mapping 3654 3006
 switchport vlan mapping 3755 3005
 switchport vlan mapping 3795 3002
 switchport vlan mapping 3843 3001
 no ip address
 load-interval 60
 speed nonegotiate
 no cdp enable
 no mop enabled
 spanning-tree bpdufilter enable 


int vlan3001 
  ip address blah
  do something useful;
int vlan 3002
   same
...

int g4/46 
  switchport 
  switchport access vlan 3005
  switchport mode access

----------------------------

In other words, some ckts I terminate L3 on the 6500, and some I pass
through as L2 to other devices. 


A new ckt/VLAN-appearance is being installed. I'd _really_ like to be
able to use it as a dot1q trunk to the other site.

(The other site will just be a gig line into a switch and I can trunk
away, on that end. The provider is doing EoMPLS and will happily support
double-tagging.) 

Q-in-Q seems straightforward, if I was using sub-interfaces and
terminating all of the ckts on the 6500 - encapsulation dot1q blah
second-dot1q blabla. But I'm not, and I can't (or don't think I can),
because I _have_ to pass at least one of the point-to-points through as
L2 to another device. 

Is there a way to do this or am I whistlin' in the breeze? 

Thanks,
-bacon