User guide

6-2 MPLS Module Installation and User Guide

MPLS and IP Routing

Routing Using LSPs

This section describes the following topics:

• Routing Using Direct and Indirect LSPs on page 6-2

• LSP Precedence and Interaction on page 6-4

• Equal Cost LSPs on page 6-4

• Overriding IBGP Metrics for RSVP-TE LSPs on page 6-5

Routing Using Direct and Indirect LSPs

Using MPLS, two types of LSPs can be used to route a packet to its destination:

• Direct LSP

An LSP is considered direct with respect to an FEC if it has been associated with the

FEC via LDP or RSVP-TE.

• Indirect LSP

An LSP is considered indirect with respect to an FEC if it has been associated with

the FEC via a routing protocol.

Figure 6-1 illustrates the concept of direct and indirect LSPs.

Figure 6-1: Direct and indirect LSPs

Subnet

MPLS_17

LSR A

Router ID

10.3.1.1

LSR B

Router ID

10.2.1.1

LSR C

Router ID

10.1.1.1

10.0.1.0/24

10.0.2.0/24

10.0.3.0/24

Bound labels

for LSR A

Direct

LSPs

Subnet