Hi Alan,
If OSPF, EIGRP and RIP have learned the 192.168.0.0/24 route then only one will be installed in the routing table. EIGRP will be selected since it has the lowest administrative distance.
By default, LDP will generate a label for each route in the routing table. This is something that you can change by using access-lists if you want.
The LFIB has pretty much the same information as the FIB, however some entries in the FIB (like directly connected interfaces) won’t show up in the LFIB.
Theoretically, switching based on labels is faster than routing where we do a lookup for the IP destination. Nowadays this doesn’t matter much. Keep in mind MPLS is already quite old.
The RIB only has the best routes in it, the FIB is built with information from the RIB. That’s why you know that we also use the best path with label switching. Labels are advertised between routers, that’s how they know which label to use.
If you want to see this in action, boot a couple of routers and configure OSPF on EIGRP on them…advertise some loopbacks. Then enable MPLS on the interfaces and take a look at the different tables:
- show ip route = RIB
- show ip cef = FIB
- show mpls ldp bindings = LIB
- show mpls forwarding-table = LFIB
Rene