Lfib Table Look Up Process - Cisco Catalyst 8540 MSR Configuration Manual

Atm switch router software configuration guide

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Table of Contents

MPLS Overview

Figure 16-5 Summary Route Propagation Between LSRs

172.68.10/24

172.68.44/24

LFIB Table Look Up Process

destination over an ATM MPLS network. AdminLSR1 is the ingress point for packets from the router

AdminRt1. When the LSR receives the packet it determines the FEC and determines the LSP to use by

looking in the LFIB table.

The LFIB table is propagated using the LDP discover mechanism shown in

AdminLSR1 adds the label (VPI/VCI) 65,180 to the packet and forwards the packet out ATM interface

0/1/0. The intermediate LSR (NetLSR2) takes the labeled packet and pairs the incoming interface and

label and then uses a lookup table to determine the outgoing interface and label. After swapping the

incoming label with the new outgoing label the packet is forwarded out to the next LSR.

The label swapping process is continued at each LSR until the last LSR. The egress LSR performs the

same look up as the intermediate LSRs but the outgoing label is stripped off and the packet is either

routed or switched using Layer 3 to its destination.

ATM Switch Router Software Configuration Guide

Use label "implicit-null"

for FEC 172.68/16

shows the packet transmission and LFIB table look up process used between a source and

Use label "65,180"

for FEC 172.68/16

Configuring Tag Switching and MPLS

Use label "85,220"

for FEC 172.68/16

Catalyst 8510 msr Lightstream 1010