Cisco CRS-1 - Carrier Routing System Router Troubleshooting Manual page 251

Chapter 13 Troubleshooting Load Balancing
This shows that Router B selected GigabitEthernet0/6/5/5 as the single path to 10.1.2.1. Use the show
cef command to view the corresponding CEF path:
RP/0/RP0/CPU0:RouterB# show cef ipv4 10.1.2.1
Fri Sep 19 11:00:21.846 PST DST
10.1.2.1/32, version 0, internal 0x40040001 (0xa9482f74) [1], 0x0 (0xa902a9cc), 0x4400
(0xa94f3300)
Updated Sep 19 06:49:40.562
remote adjacency to GigabitEthernet0/6/5/5
Prefix Len 32, traffic index 0, precedence routine (0)
via 10.12.48.1, GigabitEthernet0/6/5/5, 4 dependencies, weight 0, class 0
This verifies that CEF also uses GigabitEthernet0/6/5/5 as the egress interface for traffic forwarded to
10.1.2.1. No load balancing can occur in this configuration because there are three parallel links, but
only one is allowed.
Checking the Maximum Paths
Use the maximum-paths sub-command in the OSPF configuration mode to allow up to three paths in
the routing table:
RP/0/RP0/CPU0:RouterB# configure
Fri Sep 19 11:33:27.451 PST DST
RP/0/RP0/CPU0:P2_CRS-8(config)# router ospf 200
RP/0/RP0/CPU0:P2_CRS-8(config-ospf)# maximum paths 3
RP/0/RP0/CPU0:P2_CRS-8(config-ospf)# end
Use the show route command to confirm that the routing table contains the desired number of paths:
RP/0/RP0/CPU0:RouterB# show route 10.1.2.1
Fri Sep 19 11:36:23.345 PST DST
Routing entry for 10.1.2.1/32
Known via "ospf 200", distance 110, metric 2, type intra area
Installed Sep 19 11:34:04.284 for 00:02:19
Routing Descriptor Blocks
No advertising protos.
OSPF allows equal cost load balancing only, so one of the three paths must have a higher cost. To balance
loads among links with unequal cost metrics, use Enhanced Interior Gateway Routing Protocol or
Interior Gateway Routing Protocol (EIGRP/IGRP) as your Interior Gateway Protocol (IGP).
OL-21483-02
next hop 10.12.48.1
remote adjacency
local label 16071
10.12.48.1, from 10.1.2.1, via GigabitEthernet0/6/5/5
Route metric is 2
10.12.44.1, from 10.1.2.1, via GigabitEthernet0/6/5/6
Route metric is 2
Configuration Examples for Troubleshooting Load Balancing
labels imposed {None}
Cisco IOS XR Troubleshooting Guide for the Cisco CRS-1 Router
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