Use cases of QinQ on L3 interface

sergeyrar · August 31, 2015, 02:03:09 AM

Hi,

Generally QinQ is a L2 technology which allows service providers to extend it's clients virtual broadcast domains across their sites, without interfering with each others VLANs.

Recently I found out that QinQ can be also implemented on L3 interfaces,
Does anyone have any information regarding some designs where it may be applicable?

Thanks,

wintermute000 · August 31, 2015, 02:43:30 AM

que? Can you elaborate?
double tagging dot1q by definition is at layer 2, not sure what you mean by L3.

and i would disagree with your assessment of usage - its normally used to allow clients to tag vlans (customer inner vlans encapsulated within the provider outer vlan) in a metro ethernet network e.g. VPLS or L2VPN.

sergeyrar · August 31, 2015, 03:23:51 AM

Sure,

It's kind of similar to a router on a stick functionality, which routes packets between dot1q L3 interfaces.

I just wonder what could be the use cases of QinQ on a L3 interface and why does it exist ?? ( specifically in service provider routers )

- About the L2 part - we kinda meant the same thing, maybe I wasn't so clear ^__^

sergeyrar · August 31, 2015, 08:12:12 AM

Found some interesting application for it - view attachment.

In L3vpn scenario, one PE router with the help of QinQ can service more than 4094 clients (dot1q limitation).

deanwebb · August 31, 2015, 09:24:46 AM

That is some crazy stuff, there.

srg · August 31, 2015, 11:42:06 AM

Sometimes you can use QinQ internally, or get a double tagged QinQ handoff from provider, and be able to terminate it on a L3 interface is then pretty nice, instead of having to somehow pop one VLAN and single terminate it. Cisco does this on routers with 'encapsulation dot1q XYZ second-vlan ABC'

that1guy15 · August 31, 2015, 07:48:26 PM

Oh god why!?!

Please stop. just dont....

Reggle · August 31, 2015, 11:33:55 PM

Ooh. EVC on Metro switches.
I used QinQ L3 interfaces for management at one point. But you can route with it if you want I guess.

srg · September 01, 2015, 01:00:30 AM

Quote from: that1guy15 on August 31, 2015, 07:48:26 PM
Oh god why!?!

Please stop. just dont....

Can't really scale vlan per customer services without it. Or any other scenario where you want to abstract away the actual vlan used.

What do you think is wrong with it?

that1guy15 · September 01, 2015, 07:54:56 AM

The complexity of managing and maintaining this type of environment.

I guess if I saw an actual deployment it might come across better.