Specifications

mpls ldp explicit-null
MP-218
Cisco IOS Multiprotocol Label Switching Command Reference
January 2010
Usage Guidelines Normally, LDP advertises an Implicit Null label for directly connected routes. The Implicit Null label
causes the previous hop (penultimate) router to do penultimate hop popping. Situations exist where it
might be desirable to prevent the penultimate router from performing penultimate hop popping and to
force it to replace the incoming label with the Explicit Null label.
When you issue the mpls ldp
explicit-null command, Explicit Null is advertised in place of Implicit
Null for directly connected prefixes permitted by the prefix-acl argument to peers permitted by the
peer-acl argument.
If you do not specify the p
refix-acl argument in the command, Explicit Null is advertised in place of
Implicit Null for all directly connected prefixes.
If you do not specify the p
eer-acl argument in the command, Explicit Null is advertised in place of
Implicit Null to all peers.
Examples The following command shows how to cause Explicit Null to be advertised for all directly connected
r
outes to all LDP peers:
Router(config)# mpls ldp explicit-null
The following command sequence shows how to cause Explicit Null to be advertised for directly
connected route 10.5.0.0 to all LDP peers and Implicit Null to be advertised for all other directly
c
onnected routes:
Router(config)# mpls ldp explicit-null
Router(config)# ip access-list standard adv-exp-null
Router(config-std-nacl)# permit 10.5.0.0
Router(config-std-nacl)# deny any
Router(config-std-nacl)#
Related Commands Command Description
show mpls ip binding Displays specified information about label bindings learned by LDP.