Step 1: Configure One-to-One Backup

The following steps show the commands you must issue to configure a LSP with fast reroute and a primary path. The show command output includes bandwidth and hop limit for your information only. Bandwidth and hop limit are not configured on R1. You can configure bandwidth and hop limit using the bandwidth and hop-limit statements at the [edit protocols mpls lsp lsp-path-name] hierarchy level.

NOTE: It is not necessary to issue the fast-reroute statement on the transit or egress routers.

Action

To configure one-to-one backup on the ingress router, follow these steps:

1. In configuration mode, go to the following hierarchy level:

[edit]

user@R1# edit protocols mpls 

2. Configure the LSP:

[edit protocols mpls]

user@R1# set label-switched-path lsp-path-name to address

For example:

[edit protocols mpls]

user@R1# set label-switched-path r1-to-r5 to 192.168.5.1 

3. Configure one-to-one backup (fast reroute):

[edit protocols mpls]

user@R1# set label-switched-path lsp-path-name fast-reroute 

For example:

[edit protocols mpls]

user@R1# set label-switched-path r1-to-r5 fast-reroute 

4. (Optional) Configure a primary path:

[edit protocols mpls]

user@R1# set label-switched-path lsp-path-name primary primary-name 

For example:

[edit protocols mpls]

user@R1# set label-switched-path r1-to-r5 primary via-r2 

5. (Optional) Configure the primary ERO list:

[edit protocols mpls]

user@R1# set path path-name address loose

For example:

[edit protocols mpls]

user@R1# set path via-r2 10.0.12.14 loose

6. Verify and commit the configuration:

[edit protocols mpls]

user@R1# show

user@R1# commit

Sample Output

[edit protocols mpls]

user@R1# show 

label-switched-path r1-to-r5 {

    to 192.168.5.1;

    fast-reroute;

    primary via-r2;

    bandwidth bps; # Bandwidth for the LSP

    hop-limit number; # Maximum number of routers the LSP can 
                                           traverse

}

path via-r2 {

    10.0.12.14 loose;

}

[...Output truncated...]

[edit protocols mpls]

user@R1# commit 

commit complete

What It Means

When the fast-reroute statement is configured, the ingress router signals all downstream routers to compute and preestablish a detour path for the LSP, using the Constrained Shortest Path First (CSPF) algorithm on the information in the local router's traffic engineering database (TED). By default, when the detour path is calculated by CSPF, the detour path inherits the same administrative group constraints (link coloring or resource classes) as the main LSP.