R2 and R5 are PE routers. R0,R1, R6 and R7 are CE routers.
So, here are the basic steps we need to do for MPLS-VPN.
- In the MPLS core network, enable any IGP (OSPF) and advertise loopback IP address of all routers.
- Enable LDP session between adjacent routers. Make sure, the router ID is reachable to bring the LDP neighborship UP.
- Establish iBGP session among PE routers using “vpnv4/6” address family.
- Configure VRF with appropriate RD / import and export RT on PE routers.
- Enable interfaces facing CE with appropriate VRF (ip vrf forwarding <name>) and then assign IP address.
- Configure PE_CE routing protocol with above vrf (router ospf <x> vrf <name>)
- Configure the routing protocol on the CE router. (router ospf <x>)
- Redistribute OSFP VRF under “ipv4 vrf” address family of BGP process. This makes site-1 ospf routes to redistribute as vpnv4 routes among PE routers.
- On the egress PE side, redistribute BGP routes into “router ospf <x> vrf <name>” so that site-1 OSPF routes are redistributed as type-3 LSA(if same area) to site-2
- Vice versa, above 2 steps to make site-2 OSPF routes to available to site-1.
- Test ping from site-1 to site-2 route and vice versa. Also, use “ping vrf” from PE routers.