1. Configure the LSP

Action

To configure an LSP in your network, follow these steps:

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

[edit]

user@host# edit protocols mpls

2. Configure the LSP on the ingress and egress routers:

[edit protocols mpls]

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

3. Verify and commit the configuration:

user@host# show

user@host# commit 

Sample Output 1

user@R1> edit

Entering configuration mode

[edit]

user@R1# edit protocols mpls

[edit protocols mpls]

user@R1# set label-switched-path R1-to-R6 to 10.0.0.6

[edit protocols mpls]

user@R1# show 

label-switched-path R1-to-R6 {

    to 10.0.0.6;

}

interface all;

interface fxp0.0 {

    disable;

}

[edit protocols mpls

user@R1# commit 

commit complete

Sample Output 2

[edit protocols mpls]

user@R6# show 

label-switched-path R6-to-R1 {

    to 10.0.0.1;

}

interface all;

interface fxp0.0 {

    disable;

}

What It Means

The sample output shows that two CSPF LSPs (R1-to-R6 and R6-to-R1) are configured between routers R1 and R6. CSPF is enabled by default with the JUNOS software. The example network shown in Figure 1 focuses on CSPF LSPs.

The CSPF algorithm is an advanced form of the SPF algorithm used in OSPF and IS-IS route computations. CSPF is used in computing paths for LSPs that are subject to multiple constraints. When computing paths for LSPs, CSPF considers not only the topology of the network, but also the attributes of the LSP and the links, and attempts to minimize congestion by intelligently balancing the network load.

Typically in a network, LSPs are configured to every other egress router, resulting in a full mesh of LSPs that correspond to the BGP full mesh. In the example network shown in Figure 1, two LSPs are configured between R1 and R6 to allow for bidirectional traffic. The first LSP is from R1 to R6 (R1-to-R6) and the second is from R6 to R1 (R6-to-R1). If only one LSP was configured, for example, from R1 to R6, only unidirectional traffic would be allowed.