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Cisco Q-in-Q versus dot1ad on NNI ports

Dear community,

Is it possible to deploy a switch with NNI interfaces where a different S-tag Ethertype
is used on different ports?  I mean, Cisco's Q-in-Q on the one port (Ethertype 0x8100)
and IEEE dot1ad on the other (Ethertype 0x88a8).

The switch is supposed to switch the traffic between the ports, based on the S-Vlan

only.  There are no UNI ports (popping/pushing of S-Vlan headers).

The switching may be either via conventional bridging or via
EVC.  For the first switching method, I think it should be possible

on ME3400E or on Cat6k.

* Cat6k         : using trunk ports with 'switchport dot1q ethertype 8100' (default) and

                      'switchport dot1q ethertype 88a8' respectively

* ME3400E   : using trunk ports with 'ethernet dot1ad nni' configured, and without

                      that configuration

                      For ME3400E there is an explicit warning not to do this for
                      common Vlans (this is precisely what is the intention here),
                      does anybody understand why?  What I want is very simple,
                      no UNI's on this switch and not any L2 protocol tunneling.

For the second method (EVC), I don't have much hope for the platforms that

I looked into (Cat6k-Sup2T and ME3600X).  It is nowhere documented which

outer Ethertype is used, but I assume that they support only 0x88a8 on Cat6k and

only 0x8100 on ME3600X.  Can anybody confirm that?

IOS syntax on Cat6k-Sup2T (service mode)

     enapsulation dot1q 22-44

     rewrite ingress tag push dot1ad 10 symmetric

IOS syntax on ME3600X (config manual mentions 'Cisco QinQ Ethertype for S-tags')

    rewrite ingress tag push dot1q ...

Ideally we can also do Vlan translation of the S-Vlans. Currently I use a Cat4k (Sup7) which

does that nicely, but the Cat4k seems to only support only (I would be glad if somebody can

correct me here...).  EVC seems promising, but I haven't deployed it anywhere.

Many questions here... thanks in advance for the support.

Patrick De Muynck

Space Hellas - Athens - Greece

CCIE 8282

1 Accepted Solution

Accepted Solutions

Yes - you are right - I've corrected it. It was a Copy & Paste error. Thank you.

View solution in original post

4 Replies 4

Level 1
Level 1

Hi Patrick,

we solved this problem through a temporary solution with a Cat6500E Sup720T with two interfaces between the NNI-Port and the ME3600X:

NNI-Port <--0x88a8---> Cat6500E <---0x8100---> ME3600X


interface GigabitEthernet1/3/2

description NNI-Uebergabe  Ethernet P2MP Ethertype


switchport trunk encapsulation dot1q

switchport dot1q ethertype 88A8

switchport trunk allowed vlan 650-698

switchport mode trunk

mtu 9198

interface GigabitEthernet1/3/1

description Normal Trunk to ME3600X


switchport trunk encapsulation dot1q

switchport trunk allowed vlan 650-698

switchport mode trunk

mtu 9198


But we are still waiting for Ethertype 0x88A8-Support in ME3600X.

Kind regards,


Nachricht geändert durch Christoph Rockenstein - there was a copy&paste error in Gig 1/3/2

Should that be 'switchport dot1q ethertype 88a8' under the Gi1/3/2?  I believe that the ethertype parameter is missing, right?

Yes - you are right - I've corrected it. It was a Copy & Paste error. Thank you.

Thank you