[c-nsp] QinQ termination on a Catalyst 6800

sthaug at nethelp.no sthaug at nethelp.no
Mon Feb 18 13:13:44 EST 2019

> Cat6K and 6880 support QinQ.
> We use it to connect  some L3 vlans between our DC.
> I’m not at my desk, but from memory, ..
> 1) on the access port facing the ‘client’ ….
> Switchport mode dot1q-tunnel
> switchport access vlan xxx.    Where xxx is the transport/service provider side vlan assigned to this client.
> 2) add the above ‘xxx’ transport vlan to any dot1q trunks used between client sites.

Note well the difference between

- QinQ: An extra (outer) VLAN tag is added to ingress Ethernet frames
which already contain one or more VLAN tags. Example configuration is
"switchport mode dot1q-tunnel" + "switchport access vlan X".

- Double VLAN tag termination: An Ethernet service (e.g. IP based) is
terminated on the Catalyst switch based on both outer (SVLAN) and inner
(CVLAN) tags. Example config is "encapsulation dot1Q X second-dot1q Y".

As far as I know, Cat 6500 supports the former but not the latter. I
have no experience with the 6880.

Steinar Haug, Nethelp consulting, sthaug at nethelp.no

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