Cisco Catalyst 4000 series Hardware Troubleshoot page 14

3. Capture the show config and show logging buffer 1023 command output. The show config
command shows only the non−default configuration changes. Ideally, every time you make a change,
you should have backed−up the configuration to use as a comparison. Issue the show config
command in order to possibly associate a configuration change with the behavior you experience.
If you see any system messages other than informational messages that can indicate a hardware or
some other problem, issue the show logging buffer 1023 command in order to capture these
messages. This command displays the last 1023 system messages with timestamps, by default. Also,
refer to Messages and Recovery Procedures well as Common CatOS Error Messages on Catalyst 4000
Series Switches in order to see if you can rule out any harmless system messages from those that can
indicate a problem. Use the Error Message Decoder tool in order to help decipher the output of any
messages.
4. Many performance related problems are related to network traffic conditions. Capture the show
system command output in order to see if this is a network traffic problem.
The show system command can be used to check the current backplane utilization, which is typically
less than ten percent. If you believe that you are having performance related issues on a particular
switch, look at the Peak field, which is the peak backplane utilization on the switch since it was last
booted, and note the timestamp indicated by Peak−Time. Keep in mind that spikes in traffic
percentage on the backplane can be a STP loop or broadcast storm. Refer to Spanning Tree Protocol
Problems and Related Design Considerations for more information.
5. Capture the show proc cpu command output. This command helps identify a process that can cause
high CPU utilization on the supervisor. This is an excerpt of show proc cpu command output:
Cat4000−c> (enable) show proc cpu
CPU utilization for five seconds:
PID Runtime(ms) Invoked
−−− −−−−−−−−−−− −−−−−−−−−− −−−−−−−− −−−−−−− −−−−−−− −−−−−−− −−− −−−−−−−−−−−−−−−
1 20176816
When you view the output of this command, remember that the CPU utilization is the first thing
shown. Do not confuse the Kernel and Idle amount as CPU utilization. The Kernel and Idle is the
percentage of CPU that was idle for that time frame. Therefore, in the past five minutes, only 11.62
percent of the CPU was utilized, which is within typical boundaries.
Refer to Understanding CPU Utilization on Catalyst 4000, 2948G, 2980G, and 4912G Switches for
more information and a complete understanding of how the CPU is utilized on Catalyst 4000, 2948G,
2980G, and 4912G switches.
Complete these steps in order to get a baseline of your switch and help identify which process can
cause a problem:
♦
Issue the show proc cpu command during a time of normal activity for your network. Save
the results.
♦
Run this command again if you experience any performance related issues.
♦
Compare the two outputs. Is there a process you can identify that is unusually high in
comparison?
♦
Run the command multiple times. Is there a significant increase or decrease in CPU
utilization or spikes? Or, does CPU utilization remain consistently high?
The answer is most likely not a hardware problem, but points elsewhere.
6. One performance related issue that results from misconfiguration is when the inband channel, which
is used for any control traffic terminating on the switch such as ping, Telnet, VLAN Trunk Protocol
(VTP), STP, CDP, and so forth, is not put in a separate VLAN from user data.
11.62%
one minute: 12.00%
five minutes: 12.00%
uSecs
0 0
5Sec 1Min 5Min
88.38% 88.00% 88.00% −2
TTY Process
Kernel and Idle