Cisco CRS-1 - Carrier Routing System Router Troubleshooting Guide

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Cisco IOS XR Troubleshooting Guide for the Cisco CRS-1 Router
OL-21483-02
Chapter 13 Troubleshooting Load Balancing
Configuration Examples for Troubleshooting Load Balancing
Troubleshooting Layer 3 or Layer 4 Load Balancing Example
Table 13-1 shows the sample configuration that this section uses to describe the troubleshooting process.
Two routers, Router A and Router B, connect back to back over three serial Gigabit Ethernet interfaces.
The bold text identifies those configurations that affect load balancing.
Verifying Parallel Links in the Routing Table
Troubleshooting of load balancing starts with the routing table, as described in the following sections:
• Checking the IGP Routing Table
• Checking the Maximum Paths
• Checking the Route Metric
Checking the IGP Routing Table
This section shows how Router B selects one or more paths to reach Router A's loopback interface,
10.1.2.1.
By default, Open Shortest Path First (OSPF) supports four equal-cost paths to a destination. In this
scenario, Router B is configured with maximum-paths equal to one, so it chooses only one path from the
possible equal-cost paths. Use the show route command to view the current path to Router A:
RP/0/RP0/CPU0:RouterB# show route 10.1.2.1
Fri Sep 19 11:02:00.732 PST DST
Routing entry for 10.1.2.1/32
Known via "ospf 200", distance 110, metric 2, type intra area
Installed Sep 19 06:49:40.555 for 04:12:20
Routing Descriptor Blocks
10.12.48.1, from 10.1.2.1, via GigabitEthernet0/6/5/5
Route metric is 2
No advertising protos.
Table 13-1 Sample Configuration
Router A Router B
interface GigabitEthernet0/6/5/5
ipv4 address 10.12.48.1 255.255.255.0
!
interface GigabitEthernet0/6/5/6
ipv4 address 10.12.44.1 255.255.255.0
!
interface GigabitEthernet0/6/5/7
ipv4 address 10.12.40.1 255.255.255.0
router ospf 200
!
area 0
!
interface GigabitEthernet0/6/5/5
interface GigabitEthernet0/6/5/6
interface GigabitEthernet0/6/5/7
cost 10
interface GigabitEthernet0/6/5/5
ipv4 address 10.12.48.2 255.255.255.0
!
interface GigabitEthernet0/6/5/6
ipv4 address 10.12.44.2 255.255.255.0
!
interface GigabitEthernet0/6/5/7
ipv4 address 10.12.40.2 255.255.255.0
router ospf 200
maximum-paths 1
area 0
!
interface GigabitEthernet0/6/5/5
interface GigabitEthernet0/6/5/6
interface GigabitEthernet0/6/5/7
cost 10

Cisco CRS-1 - Carrier Routing System Router Specifications

General

Brand	Cisco
Model	CRS-1 - Carrier Routing System Router
Category	Network Router
Language	English