Sporadic High Cpu - Cisco 1841 - Version 15.0(1)

[bruno.trombim]

Hi Guys,

 i am having a few peaks during the day on a Cisco router, we are suspecting that when we send a charge to the point card the router CPU increases dramatically, we believe that the process works with many small files and the router needs to process all them at the same time, would i have any tool that I can put in the router interface to check those packets in and out to get them to analyze,  the problem is sporadic and would need something monitoring 24 hours and that does not impact the router performance.

best regards,

[Palani Mohan · Accepted solution]

Hi Bruno

Generally speaking, CPU usage is the equivalent of a Speedometer is for a car. It tells you how fast you are traveling.

When it comes to CPU utilization, it is not uncommon that high-CPU (even low 90s, for short duration) is not known to cause service interruption. Stated differently, when CPU is the bottleneck, you will notice that you are unable to Telnet/SSh to the router OR if you do, the response is sluggish, ICMP/SNMP response are erratic (frequent timeouts) etc.

Cisco routers (running IOS) spend CPU cycles to:

• service interrupts
• service processes

To make progress, you need to determine if the CPU is high due to interrupts OR process(es). For this, please consider adding the following config:

!
process cpu threshold type total rising 90 interval 10 falling 60 interval 10
process cpu threshold type interrupt rising 60 interval 10 falling 40 interval 10
process cpu threshold type process rising 75 interval 10 falling 60 interval 10
!

These cmds trigger a syslog when the CPU rises and falls. The syslog message sample would look something like:
%SYS-1-CPURISINGTHRESHOLD: Threshold: Total CPU
Utilization(Total/Intr): 90%/85%, Top 3 processes(Pid/Util):  61/2%, 125/1%, 2/0%

From this message, we can be informed about:
Total CPU utilization
Amount of CPU spent servicing interrupts
Top 3 processes PID# with # CPU utilized by these processes
How long the condition lasted

Most important: Are you actively troubleshooting any performance issues? Are any of your users complaining slow performance?

Palani

[bruno.trombim]

Thanks Palani,

thanks for the whole information, i already added those line in my router to monitor whether the problem are processes or even interrupts then late i post the results.

thanks

bruno trombim