09-05-2008 01:18 PM - edited 03-03-2019 11:26 PM
I have a 1841 running on c1841-spservicesk9-mz.124-7d.
I see more than 80% of CPU utilization soon after saving the configuration(write mem), which lasts for several seconds. Could this lead to a router crash at a particular stage?
Is it due to a bug in IOS?
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09-06-2008 01:27 AM
Hello Ranil,
the cpu on a router like yours can have these spikes.
About why saving the config can cause a so high cpu usage I think that modern routers that are SDM ready can actually have to create an XML file for the running config, then they have to translate it to a simple text file and to write it on the NVRAM.
So the duty can be now heavier then in the past.
I usually look at the cpu average 1min as the parameter to decide if a router is working fine or it is overloaded.
Hope to help
Giuseppe
09-05-2008 01:30 PM
Router crashes are due to software bugs, not hardware utilization. The 1800's are small routers and use a lower end processor. My 1800's do the same and I have never had a problem with them yet.
Hope that helps.
09-05-2008 01:31 PM
Hello Ranil,
if the cpu goes over 80% only for several seconds it shouldn't lead to a router crash.
Is it due to a bug in IOS?
It may be after having seen a bug about HSRP in your other post ...:)
Hope to help
Giuseppe
09-05-2008 02:17 PM
Hi Giuseppe,
You are quite right. In fact, I came across another bug which says router crashes when the write memory and
secure boot-image commands are executed simultaneously(Ref: CSCsg69124).
I've been thinking since about a week regarding this high CPU utilization when saving the runnging config.
When I noticed that it consumes lot of processing power, I was a bit suspicious that this symptom also has something to do with the affected image.
So do you mean to say that this normal and expected?
FYI: the average CPU utilization is around 2% at the moment.
09-05-2008 04:19 PM
It's likely normal behavior, since many Cisco software based routers spike their CPU when writing to the flash, such as loading a new IOS via tftp or FTP. Plus, the CPU might have to parse out the config before it saves it (often there's a delay before a show run vs. a show config.)
09-06-2008 01:27 AM
Hello Ranil,
the cpu on a router like yours can have these spikes.
About why saving the config can cause a so high cpu usage I think that modern routers that are SDM ready can actually have to create an XML file for the running config, then they have to translate it to a simple text file and to write it on the NVRAM.
So the duty can be now heavier then in the past.
I usually look at the cpu average 1min as the parameter to decide if a router is working fine or it is overloaded.
Hope to help
Giuseppe
09-08-2008 08:00 AM
Hi,
Many thanks for sharing your experiences and thoughts . I'm convinced that this is expected for an SDM enabled low-end ISR.
I've made an IOS upgrade as well(to correct the HSRP bug); CPU utilization remains the same as it was before.
Regards,
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