MPLS LDP session protection and mpls ldp neighbor ip-addr targeted command

[abgromov]

Hi all!

Normally LDP neighbors are found automatically by sending UDP Hello packets on Port 646 with the destination of multicast address 224.0.0.2 out of each LDP enabled interface. With mpls session protection a targeted LDP session must be established.

In such case Hello packets are sent as unicast packets using UDP on port 646 and destined to the targeted peer.

But it is not required to use mpls ldp neighbor ip-addr targeted command to configure session protection.

How  is session  destination  IP address determined?

Why do I not need  to specify session destination IP with mpls ldp neighbor ip-addr targeted command?

[Sandip Rathod]

Hi

Please read below quote, I hope this will answer your question

MPLS LDP Session Protection uses LDP Targeted Hellos to protect LDP sessions. Take, for example, two directly connected routers that have LDP enabled and can reach each other through alternate IP routes in the network. An LDP session that exists between two routers is called an LDP Link Hello Adjacency. When MPLS LDP Session Protection is enabled, an LDP Targeted Hello Adjacency is also established for the LDP session. If the link between the two routers fails, the LDP Link Adjacency also fails. However, if the LDP peer is still reachable through IP, the LDP session stays up, because the LDP Targeted Hello Adjacency still exists between the routers. When the directly connected link recovers, the session does not need to be reestablished, and LDP bindings for prefixes do not need to be relearned.

http://www.cisco.com/c/en/us/td/docs/ios/mpls/configuration/guide/12_2sy/mp_12_2sy_book/mp_ldp_sessn_prot.html

Let me know if you have further query

Regards,

Sandip