MPLS LDP advertise lable

mpls ldp advertise-label 


This command is enable by default. The MPLS router will advertise every network it learnt or connected network to its neighbor. In order to stop this advertisement, we use  "no mpls ldp advertise-label " However, this command will disable every advertisement in the network.

If we want to specifically advertise label for specific network to specific destination, we can use the command as followings.
      mpls ldp advertise-lable for <dest prefix>  to <ldp peer>

Example

As shown in the figure, R1, R2 and R3 are in the MPLS network. In this scenario, we specify what prefix and what destination we want to have label advertised for the MPLS network. R1 will advertise label for 1.1.1.1/32 only but not 10.10.10.10/32. Here is the configuration example on R1

( we omitted the IGP configuration )

Before configuration

R2#sh mpls forwarding-table

Local  Outgoing    Prefix            Bytes tag  Outgoing   Next Hop

tag    tag or VC   or Tunnel Id      switched   interface

16     Pop tag     30.30.30.30/32    570        Fa0/1      192.168.2.2

17     Pop tag     3.3.3.3/32        0          Fa0/1      192.168.2.2

18     Pop tag     10.10.10.10/32    0          Fa0/0      192.168.1.1

19     Pop tag     1.1.1.1/32        0          Fa0/0      192.168.1.1

Configuration command

no mpls ldp advertise-labels

mpls ldp advertise-labels for 2 to 1

access-list 1 permit 192.168.1.2

access-list 2 permit 1.1.1.1

Result / Verification

R2#sh mpls forwarding-table

Local  Outgoing    Prefix            Bytes tag  Outgoing   Next Hop

tag    tag or VC   or Tunnel Id      switched   interface

16     Pop tag     30.30.30.30/32    570        Fa0/1      192.168.2.2

17     Pop tag     3.3.3.3/32        0          Fa0/1      192.168.2.2

18     Untagged    10.10.10.10/32    0          Fa0/0      192.168.1.1

19     Pop tag     1.1.1.1/32        0          Fa0/0      192.168.1.1

We can see now that the 10.10.10.10/32 label is not advertised to R2 from R1