Another type of overlay networking is QinQ tunnelling.
QinQ involves use multiple VLAN tags in an Ethernet header so that one VLAN ID can carry another 4096 VLAN IDs in a second tag. This makes a simple and useful tunnelling strategy.
The first/inner tag is the one set by the customer, and the second/outer tag would be set by the network. It’s common in the Service Provider industry 1 to refer to these as Customer VLAN and Service VLAN
|Tag Location||Tag Name||VLAN Name||VLAN Abbreviation / Acronym|
|Inner Tag||Customer Tag||Customer VLAN||cVLAN|
|Outer Tag||Service Tag||Service VLAN||sVLAN|
- who are the only people who can deploy QinQ reliably since they don’t have to handle the loops – that’s still a customer problem. ↩