Cisco CRS-1 - Carrier Routing System Router Troubleshooting Manual page 93

Chapter 3 Troubleshooting Forwarding
DETAILED STEPS
Command or Action
Step 1
show route ipv4 prefix mask
Example:
RP/0/RP0/CPU0:router# show route 192.168.2.0
255.255.255.0
Step 2
show cef ipv4 prefix mask detail
Example:
RP/0/RP0/CPU0:router# show route ipv4
192.168.2.0 255.255.255.0 detail
OL-21483-02
Purpose
Displays the current routes in the Routing Information Base
(RIB).
Check the prefix and mask, as well as the next hop and
•
outgoing interface, to ensure that they are what is
expected.
• Note the timer value that shows how long the route has
been in the routing table. If the timer value is low the
route may be flapping.
A lower timer value is present when a route is installed
in the RIB for a short period of time. A low timer value
may indicate flapping. For example, if a BGP route was
being installed and removed from the RIB table every
sixty seconds, then the route is flapping.
Look for routes that have not been installed in the
routing table for very long. The route will either be
stable or flapping. If the route is flapping, contact
contact Cisco Technical Support. For Cisco Technical
Support contact information, see the
Documentation and Submitting a Service Request"
section on page viii
• Check that route is learned via the routing protocol you
are expecting it to be known via, and that the metric is
what you expect.
Displays the IPv4 Cisco Express Forwarding (CEF) table
detailed entry information.
Compare the prefix, mask, next hop ip, and outgoing
•
interface information with the information in the RIB.
The information in the RIB is displayed using the show
route ipv4 prefix mask command.
Check that the adjacency is valid or the expected type
•
of adjacency. For example, if it is a remote adjacency,
then the adjacency information exists on another node.
• Check that the expected hash (load balance) and egress
interfaces are listed.
Cisco IOS XR Troubleshooting Guide for the Cisco CRS-1 Router
Troubleshooting IPv4 CEF Information
"Obtaining
in the Preface.
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