802.1Q Tunneling (Q-in-Q) Configuration Example

Bonjour monsieur René Molenaar ; merci déjà pour le cours et je vous annonce en passant que j’ai validé mon CCNP 350-401
en effet je suis entrain de faire des révision dans le but d’un entretien d’embauche mais aussi afin de préparer le ENARSI 300-410 . ma préoccupation est celle-ci pourquoi déployer le tunnelisation 802.1Q et dans quel contexte c’est conseillé de penser à cette technologie au lieu de l’autre ( veillez m’éclairer sur une technologie similaire ) ? parce que l’on pourra me poser la question de pourquoi j’aurai opté ça au lieu de l’autre , j’espère que ma question est compréhensive ? merci d’avance

Hello Osema

Take a look at the diagram from the lesson once again:

The traffic that is sent from R1 reaches R2 on layer 2. From end to end, this is a Layer 2 connection, and thus no routing is involved.

I believe you are asking if within the ISP’s infrastructure, if you can have any routing, say between SW1, SW2, and SW3. What if that infrastructure is composed of dozens or hundreds of routers? Then it would make sense that the QinQ tunnel can be transmitted over a routed underlay infrastructure.

The answer is yes, you can do this, and you will find that ISPs will indeed have a Layer 3 underlay that carries Layer 2 traffic that goes end to end, much like QinQ does.

How would you do this? Well there are several ways. MPLS is one type of underlay network that can carry multiple types of data. Here’s a lesson that explains this further:

Alternatively, you can use L2TP to tunnel layer 2 over a Layer 3 network. This NetworkLessons note has more info on this protocol.

Another option is to use L2VPN or VPLS, again, more about which you can learn at this NetworkLessons note.

Keep in mind that all of these options are not limited to being used with QinQ, but are able to transport all types of Layer 2 traffic over a Layer 3 Underlay network.

I hope this has been helpful!