High cpu usage on 2921

[Koks]

Hi, i have a problem with 2921 cisco router

The problem with high cpu load, but it appears only when somebody from office is downloading something big (downloading or updating various  game clients)

command show processes cpu monitor interval  | exclude 0.00 not show what  exactly loads cpu to 100%.  I can see it only with snmp monitoring

[acampbell]

Hi,

Try :-

show proc cpu sorted

Look at the top talker in this list to give a clue as to what is hogging the cpu.

[Seb Rupik]

Hi there,

If the CPU utilisation value cannot  be accounted for by IOS processes then it must be attributed to CPU interrupts.

Can you share the first few lines of sh proc cpu  , this will show the split of interrupts / processes.

Also what is the output of sh interfaces switching

cheers,

Seb.

[Koks]

sh interfaces switching output in txt file

[Joseph W. Doherty]

Most of your CPU, during the last five seconds is interrupt CPU, and that's often directly due to volume of traffic. Often not much you can do to improve that, although there are a few things that can be done that might help a tiny bit.

Your overall process CPU is a bit more (relative to interrupt CPU) than I like to see, and I notice your IP Input is somewhat more than 2%. That too might bear some improvement, but overall you're likely just pushing more through your router than it was designed for.

[Leo Laohoo]

---

@Koks wrote:

The problem with high cpu load, but it appears only when somebody from office is downloading something big (downloading or updating various  game clients)

---

That means the WAN bandwidth exceeds the capacity of the router.

What is the WAN bandwidth?

[Koks]

Bandwidth for WAN is 200 Mbit/s

[Leo Laohoo]

2900 router can't support 200 Mbps.

[Koks]

Can you confirm your words somehow?

[curdubanbogdan]

The document in attach. confirms that it supports 200 Mbps. I want to know with a show interface WAN-int-id the statistics, bw and speed of the interface and a show cpu proc sorted to see what process consumes the most cpu. It could be bw overload. Traffic can be optimized with qos and acl's to block traffic to certain resources. 

[Leo Laohoo]

Are you running encryption/VPN?

And describe the WAN link:  Is this a 200/200 link (upload/download) or 200 Mbps (upload &/or download)?

[Joseph W. Doherty]

"The document in attach. confirms that it supports 200 Mbps."

Oh? Yes the 2921 can process more than 200 Mbps, as seen in table 1, but did you see figure 1 on the last page which Cisco recommends a 2921 for up to 50 Mbps WAN? Software based router performance varies much depending on the nature of your traffic and your configuration. Generally, process switched traffic consumes much more CPU, for the volume traffic, than interrupt switched traffic.

In other words, your CPU loading is likely to be expected with your traffic and configuration. Again, you might be able to reduce the load, a bit, by possibly adjusting your config and/or getting the amount of traffic going to IP Input reduced. However, likely a major decrease in CPU would require a more "powerful" ISR.