[c-nsp] QinQ termination on a Catalyst 6800

[James Bensley]

On Mon, 18 Feb 2019 at 18:14, <sthaug at nethelp.no> wrote:
>
> > 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.

^ This. 6500s can't terminate double tagged frames at layer 3. They
can perform dot1q "tunnelling" only. I looked at 6880 a few years ago,
I'm pretty sure this was one of the reasons we doing for it it, too
similar to the 6500 (including this limitation).

Cheers,
James.