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L2VPN vs L3VPN
I know that L2VPN is virtual switch, L3VPN is virtual router.
How does a customer decide whether to buy L2 or L3 VPN?
How would a customer decide to buy a physical switch or router?
An expert is a man who has made all the mistakes which can be made.
If we are talking about MPLS, where did the idea of virtual switches or virtual routers come from? I feel like I've never read that. To be fair, I've also never worked for a carrier. But, we use Layer 3 MPLS. I believe I read that if you get over a certain amount of branches, Layer 2 is no longer an option.
As for how Layer 3 works, I can tell you that you get an actual physical connection from the carrier; ethernet for example, and in our case at least it runs to a NID that the carrier owns. We simply plug a cable in from the router to the NID. There's configurations to be done, but it's just setting up the physical interface with an IP and speed/duplex settings, and then running a routing protocol and peering with the provider to exchange routes. In a nut shell, that's really it. As for Layer 3 MPLS, I have never seen that in place so I cannot really say where that comes from.
As networker said, it really depends on the deployment you want to do. Layer 3 (thertically speaking) is more scalable than a layer 2 VPN, however if you are happy to have you devices all on the same LAN, go for a layer 2 VPN. If there are design requirements to have different subnets within the MPLS network, go for a layer 3.
Network Engineer | London, UK | Currently working on: CCIE Routing & Switching