MPLS-LDP

1) To enable MPLS switching on an interface and start LDP on the same

interface, you must enter the interface-level command "mpls ip" . If you have

too many interfaces to enable MPLS on, you may use MPLS LDP auto

configuration, which is available when you run OSPF as your IGP protocol.

Under the OSPF process, enter the command "mpls ldp autoconfig" to

activate LDP/MPLS switching on all interfaces running OSPF.

2) Upon hearing from the other LDP routers, LDP learns their LDP Router IDs,

which is by default the highest Loopback IP addresses. You may change

the Router-ID by using the command 

"mpls ldp router-id <interface> force"

3) If for some reason the Loopback IP addresses are unreachable, a TCP

connection will not be established. If you want LDP to establish a TCP

connection using the physical interface IP address, use the interface-level

command "mpls ldp discovery transport-address interface"

4) Using the Router ID IP addresses as sources, two routers that heard from

each other establish a TCP transport connection using the destination port

of 646. This connection could be authenticated using an MD5 hash TCP

option. The hashing key is defined per-neighbor by using the command

mpls ldp neighbor <IP> password <password> . The IP address here is the

neighbor’s LDP Router ID. To make the use of passwords mandatory, you

need the global command mpls ldp password required .

To disable mpls labels during trace router issue command "no mpls label ttl-prop"