Command Reference Guide

50 ● mpls label advertise 3Com Router 5000 Family and Router 6000 Family
Command Reference
mpls label advertise
Purpose Use the mpls label advertise command to specify at the egress the type of the
label to be distributed to the penultimate hop.
Use the undo mpls label advertise command to restore the default.
Syntax mpls ldp advertise { implicit-null | explicit-null | non-null }
undo mpls ldp advertise { implicit-null | explicit-null | non-null }
Parameters explicit-null
Specifies at egress to distribute an explicit null label to
the penultimate hop.
implicit-null
Specifies at egress to distribute an implicit null label to
the penultimate hop.
non-null
Specifies at egress to distribute a normal label to the
penultimate hop.
Label value 0 stands for IPv4 Explicit NULL Label, which is valid only at the bottom of
label stack. That is, the label stack must be popped and forwarded as the IPv4 header.
Label value 1 stands for Router Alert Label, which is valid except at the bottom of
label stack. When receiving messages with label value 1 at the top of the label stack,
the system forwards them into local software module for further processing. If a
lower-layer label is to be forwarded, it must be put with Router Alert Label.
Label value 2 stands for IPv6 Explicit NULL Label, which is valid only at the bottom of
label stack. That is, the label stack must be popped and forwarded as the IPv6 header.
Label value 3 stands for Implicit NULL Label, which can be distributed and forwarded,
but cannot be placed in encapsulation. When LSR switches top-layer labels, it only
needs to pop the labels, but cannot replace them when using label 3 to replace the
original label.
Labels 4 to 15 are reserved.
Default By default, the implicit label is assigned to the penultimate hop
Example Specify at the egress to distribute a normal label to the penultimate hop.
[3Com -mpls] mpls label advertise non-null
View This command can be used in the following views:
■ MPLS view