The key to understanding the general idea of how MPLS VPNs work is to focus on the control plane distinctions between PE routers and P routers. Both P and PE routers run LDP and an IGP to support unicast IP routing. However, the IGP advertises routes only for subnets inside the MPLS network, with no [...]

Both ASBR1 and ASBR2 advertise defaults into the network, expecting to have the capability to route to the Internet through BGP-learned routes. In this case, ASBR2 is already up, fully converged. However, if ASBR1 reloads, when it comes back up, OSPF is likely to converge faster than BGP. As a result, ASBR1 will advertise its [...]

Frame-relay switching is simple to configure. In this example we have 2 serial ports and we want to be able to switch dlci’s between them. Serial port 1/0 connects to customerA using DLCI 100 and Serial 1/1 connects to customerB using DLCI 200. Both customers need reachability to eachother.
Simply enable frame-relay switching on your router.
# frame-relay switching
Then [...]