MPLS: Autoconfig (enable LDP on all interfaces) only available when using OSPF as IGP.
LDP send discovery packets via UDP to 188.8.131.52 (all routers) port 646. Route-ID is highest loopback but can be forced “mpls ldp route-id x.x.x.x force”. To use the physical connection of the interface (not the loopback due to lack of reachability) use this command on the interface. ” mpls ldp discovery transport-address interface”. Once communications is established, via TCP 646, authentication is verified (MD5 only). After peer is established prefix/label information is exchanged and LFIB is built.
Two Labels: Transport and VPN Label
View Transport label with “sh mpls forwarding-table” and VPN label with “sh ip bgp vpn4 vrf XXX”
OSPF on MPLS VPN: MP-BGP cloud is super area 0 (super backbone), treated as T-3 LSA’s. SAME VPN, SAME DOMAIN_ID (PROCESS ID) T3, different DomainID, T5.
Creating a Sham-Link
- Configure a separate /32 address on the remote PE so that OSPF packets can be sent over the VPN backbone to the remote end of the sham-link. The /32 address must meet the following criteria:
- Belong to a VRF.
- Not be advertised by OSPF.
- Be advertised by BGP.
You can use the /32 address for other sham-links.
- Associate the sham-link with an existing OSPF area.