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Chapter 51 Troubleshooting
Troubleshooting Tables
Troubleshooting CPU Utilization
This section lists some possible symptoms that could be caused by the CPU being too busy and shows
how to verify a CPU utilization problem. Table 51-4 lists the primary types of CPU utilization problems
that you can identify. It gives possible causes and corrective action with links to the Troubleshooting
High CPU Utilization d
ocument on Cisco.com.
Possible Symptoms of High CPU Utilization
Note that excessive CPU utilization might result in these symptoms, but the symptoms could also result
from other causes.
• Spanning tree topology changes
• EtherChannel links brought down due to loss of communication
• Failure to respond to management requests (ICMP ping, SNMP timeouts, slow Telnet or SSH
sessions)
• UDLD flapping
• IP SLAs failures because of SLAs responses beyond an acceptable threshold
• DHCP or IEEE 802.1x failures if the switch does not forward or respond to requests
Layer 3 switches:
Note Layer 3 functions are not supported on switches running the LAN base feature set.
• Dropped packets or increased latency for packets routed in software
• BGP or OSPF routing topology changes
• HSRP flapping
Verifying the Problem and Cause
To determine if high CPU utilization is a problem, enter the show processes cpu sorted privileged
EXEC command. Note the underlined information in the first line of the output example.
Switch# show processes cpu sorted
CPU utilization for five seconds: 8%/0%; one minute: 7%; five minutes: 8%
PID Runtime(ms) Invoked uSecs 5Sec 1Min 5Min TTY Process
309 42289103 752750 56180 1.75% 1.20% 1.22% 0 RIP Timers
140 8820183 4942081 1784 0.63% 0.37% 0.30% 0 HRPC qos request
100 3427318 16150534 212 0.47% 0.14% 0.11% 0 HRPC pm-counters
192 3093252 14081112 219 0.31% 0.14% 0.11% 0 Spanning Tree
143 8 37 216 0.15% 0.01% 0.00% 0 Exec
...
<output truncated>
This example shows normal CPU utilization. The output shows that utilization for the last 5 seconds is
8%/0%, which has this meaning:
• The total CPU utilization is 8 percent, including both time running Cisco IOS processes and time
spent handling interrupts
• The time spent handling interrupts is zero percent.
