Comments on: MPLS and Loopback Address http://www.rsivanandan.com/2009/02/21/mpls-and-loopback-address/ Never go to bed mad. Stay up and fight! Thu, 05 Jan 2012 08:58:20 +0000 hourly 1 http://wordpress.org/?v= By: Naeem Maniar http://www.rsivanandan.com/2009/02/21/mpls-and-loopback-address/comment-page-1/#comment-1470 Naeem Maniar Thu, 26 Feb 2009 08:18:08 +0000 http://www.rsivanandan.com/?p=390#comment-1470 Another reason is specific to Juniper (not sure about Cisco routes) Juniper Routers (by default) advertises only loopback address as an FEC which allows all LDP routers in the network to establish an LSP to the loopback address of every other router in the network. If loopback address is not configured then route id (lowest interface IP) with /32 prefix will be advertised as an FEC then receiving router will first try to locate reachbility to advertised FEC through IGP and obviously won't find reachability as address is advertised with /32 prefix, as a result no LSP will be established. Another reason is specific to Juniper (not sure about Cisco routes)

Juniper Routers (by default) advertises only loopback address as an FEC which allows all LDP routers in the network to establish an LSP to the loopback address of every
other router in the network. If loopback address is not configured then route id (lowest interface IP) with /32 prefix will be advertised as an FEC then receiving router will first try to locate reachbility to advertised FEC through IGP and obviously won’t find reachability as address is advertised with /32 prefix, as a result no LSP will be established.

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