MPLS Model

MPLS VPN Model:

As I said in last post, MPLS VPNs combines the best feature of an overlay VPN and Peer to Peer VPN.

PE router participates in customer routing guarantying optimum routing between sites with combination of easy provisioning of sites

PE routes carry a separate set of routes for each customer (similar to dedicated PE router approach, It allocates a VRF to particular customer)

Customers can use overlapping address. (Since VRF acts like a dedicated router for each customer)

The PE routers hold the routing information only for directly connected VPNs. As a result, the size of the PE routing table is significantly reduced.

MPLS VPN architecture is very similar to the dedicated PE router Peer-to-Peer model, but the dedicated per customer router are implemented as virtual routing tables within PE routers.

The whole PE router is still configured and managed as a single device, not as a set of virtual routers.

Here is a logical view of PE Router:

For more detailed information about MPLS end to end routing flow : http://startnetworks.blogspot.com/2010/07/mpls-l3-vpn-end-to-end-routing-flow.html