Troubleshooting guide

11-25
ATM and Layer 3 Switch Router Troubleshooting Guide
OL-1969-01
Chapter 11 Troubleshooting Layer 3 Network Connections
Troubleshooting IP Layer 3 Connections
Troubleshooting IP Layer 3 Connections
The Layer 3 enabled ATM switch router uses Cisco Express Forwarding (CEF). Much of the internal
troubleshooting determines whether the central CEF information in the route processor is consistent with
the distributed information in the content addressable memory (CAM) on the interfaces.
Troubleshooting an IP Layer 3 connection is separated into the following processes:
• IP Layer 3 Connection Troubleshooting Commands, page 11-25
• Checking the IP Routing Table, page 11-27
• Checking the Interface Status, page 11-28
• Checking the IP CEF Adjacencies, page 11-30
• Checking the Interface CAM Table Entries, page 11-32
Figure 11-14 shows the example network used to troubleshoot an IP Layer 3 connection in the following
examples.
Figure 11-14 IP Layer 3 Connection
In Figure 11-14, Host A is the source end station trying to communicate with Host B, the destination end
station.
IP Layer 3 Connection Troubleshooting Commands
To troubleshoot an IP Layer 3 connection problem, use the following commands:
Host A Catalyst 8540-2Catalyst 8540-1 Host B
10.85.40.0/24 10.85.66.0/24 10.85.45.0/24
.5 .254 .10 .5 .254 .5
MAC:
00:10.e3:aa...
Fast Ethernet connection (fast 1/0/15 on C8540-1)
Gigabit Ethernet connection (giga 0/0/0 on C8540-1)
MAC:
00:90.21:bb...
MAC:
00:90.21:dd...
MAC:
00:90.21:ff...
MAC:
00:90.21:cc...
MAC:
00:90.21:ee...
49994
Command Purpose
show ip route Displays routing table entries.
show controllers c8500 status Displays the status of all Ethernet processor
interfaces.
show controllers c8500 counters Displays the counters of all Ethernet processor
interfaces.
show ip cef Displays Cisco Express Forwarding
information.