[c-nsp] QinQ termination on a Catalyst 6800

[Steve Dodd]

For completeness sake, if there are a low number of S-VLANs for your use
case then an external loopback cable might suffice.

-Steve

On Tue, Feb 19, 2019 at 9:02 AM James Bensley <jwbensley at gmail.com> wrote:

> 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.
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