Ldp Shortcut For Igp Routes; Ldp Shortcut Configuration; Igp Route Resolution - Alcatel-Lucent 7450 Manual

Ethernet service switch

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LDP Shortcut for IGP Routes

The LDP shortcut for IGP route resolution feature allows forwarding of packets to IGP learned

routes using an LDP LSP. When LDP shortcut is enabled globally, IP packets forwarded over a

network IP interface will be labeled with the label received from the next-hop for the route and

corresponding to the FEC-prefix matching the destination address of the IP packet. In such a case,

the routing table will have the shortcut next-hop as the best route. If such a LDP FEC does not

exist, then the routing table will have the regular IP next-hop and regular IP forwarding will be

performed on the packet.

An egress LER advertises and maintains a FEC, label binding for each IGP learned route. This is

performed by the existing LDP fec-originate capability.

The user enables the use of LDP shortcut for resolving IGP routes by entering the global command

config>router>ldp-shortcut.

This command enables forwarding of user IP packets and specified control IP packets using LDP

shortcuts over all network interfaces in the system which participate in the IS-IS and OSPF routing

protocols. The default is to disable the LDP shortcut across all interfaces in the system.

When LDP shortcut is enabled, LDP populates the RTM with next-hop entries corresponding to all

prefixes for which it activated an LDP FEC. For a given prefix, two route entries are populated in

RTM. One corresponds to the LDP shortcut next-hop and has an owner of LDP. The other one is

the regular IP next-hop. The LDP shortcut next-hop always has preference over the regular IP

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