In a MAN, two PEs in both A and B sites have a full configuration for igp (isis), mbgp and mpls. They could learn the MPLS VPN route information advertised by the peer, but they cannot ping to each other.
1. Check if MPLS is configured correctly.
2. Check if mpls peer has been set up correctly.
3. Check if the local IGP routing table contains the specific route of the next hop address of VPN private network route.
4. Check if the specific route for the address of next hop of VPN private network route has been allocated with correct tags by routers along MPLS LSP.
Diagnosis Result: The routing table for ISIS of local PE does not contain the specific route of the address for next hop of VPN private network route.
Solution: Delete the convergence route at core equipment, and import the routing information (for example, a route with 32-bit loopback address) of level-2 at the backbone router (level-2) in the area into the database of level-1, so that the common routers in the area could learn it. Up to now, the problem has been solved.
When observing the VPN routes, we find that all the next hops point to the address of loopback0 of PE at the peer, and the IGP routing table at local does not have the specific route to the address. The possiblities include:
1. After route convergence on a backbone router, the adjacent routers could only learn the convergence route, not the specific route.
2. In deployment of ISIS, the area and the level of ISIS circuit have been planned, so the backbone router (level-2) will screen out the specific route outside the area automatically, and generate one default route for advertisement to common routers (level-1) in the area. Therefore, the local routing table does not contain the specific route of the address for next hop of VPN route of remote PE.
3. the local routing table does not contain the specific route (public network) of the address for next hop of VPN route of remote PE, so MPLS cannot allocate tags, and LSP tunnel cannot set up, so it is impossible to ping through.
In deployment of MPLS VPN, avoid route convergence as much as possible; in planning of area division for ISIS, it also needs to consider that the private network route of MPLS VPN should be borne by specific route of public network.