Understand VPLS customer Vlan manipulation and the need for QinQ

[Louey]

Hi everyone

 I am pretty new in SP networks and facing some difficulties understanding VPLS.

As I understand, VPLS is used to connect different cutomer sites on layer 2 (as if they were all connected to a switch on a the same VLAN). For this, it uses a VFI in the PE routers (connecting the customer CE routers) with a vpn id to identify the VPLS domain. VC (pseudowires) are configured between PEs to carry trafic between VFIs in the same VPLS domaine in different PEs.

Normally, a customer frame coming on a PE with vlan tag x, will be encapsulated into an VPLS/MPLS frame in order to get directed to the other PEs and then to other customer sites. Why would we need to manipulate customer vlan tag or add a second layer of vlan tag (QinQ) to the customer frame ? Can someone help understand this in depth please ?

The documentation for VPLS is not the best and no video does explain it well in depth.

Regards

[balaji.bandi]

as per i know because Many customers can have the same VLAN used (same Like we use RF1918 address space)

[Louey]

Thanks a lot for the answer.

Even if customers have the same Vlans they are normally separated into Vfi wich separate customer trafic when arriving into the PE.

Why would the customer vlan tag be relevant in the PE as the customer trafic is into separate vfi ?

Thank you

[MHM Cisco World]

CE have many VLAN it will L2VPN to other Site, is it easy for SP to map all VLAN or use Q-in-Q ?
use Q-in-Q make SP use one VLAN inside SP core that server all VLAN of costumer.

[Louey]

Thanks a lot for your reply.

Okay I understand but what I understood is that a customer trafic would be separated into a separate vfi, so normally the customer Vlan tag does not have to be taken in consideration on the PE as it is the vfi wich is important.

Even if some different customers vlans overlap they would separated by their vfi (I think of that as VPN MPLS), why would the PE see/use the customer Vlan tag as, anyway, it will be separated into a vfi ?

Can you please explain that ?

[MHM Cisco World · Accepted solution]

first there are two PE one is U-PE and other is N-PE

the VFI is config in N-PE and QinQ if I am right config in U-PE.