Cisco 3845 with high CPU and Interupt

CiscoNutt · ‎03-11-2015

I have a 3845 running IOS version 15.1(4)M8 which has very high CPU and interupt:

CPU utilization for five seconds: 73%/70%; one minute: 78%; five minutes: 75%
PID Runtime(ms) Invoked uSecs 5Sec 1Min 5Min TTY Process
64 128368276 5188871 24739 1.12% 1.15% 1.14% 0 Per-Second Jobs
362 21040940 1224481386 17 0.80% 0.91% 0.91% 0 IP SLAs XOS Even
90 2424 651 3723 0.32% 0.06% 0.01% 706 SSH Process
123 9922532 642308913 15 0.32% 0.33% 0.32% 0 Ethernet Msec Ti
223 7175980 1222858710 5 0.24% 0.28% 0.30% 0 HQF Shaper Backg
358 8225664 314776930 26 0.24% 0.23% 0.23% 0 HSRP Common
2 1738752 1037228 1676 0.08% 0.08% 0.08% 0 Load Meter
303 5476208 6197476 883 0.08% 0.08% 0.05% 0 Crypto PAS Proc
143 7143280 21090388 338 0.08% 0.07% 0.06% 0 IP Input
139 2105108 157888159 13 0.08% 0.05% 0.06% 0 IPAM Manager

The interface input / output rates are not near the Bandwidth limit of the interfaces. Our Smarteye server shows normal CPU levels. So I am wondering if this is just a cosmetic thing with the router?

It also doesn't seem to be CEF but I have not tried disabling it.

Logging show only the occasional rekey for GET VPN.

Thanks,

Joseph W. Doherty · ‎03-11-2015

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Posting

A 3845, generally, does not have the capacity for it's gig LAN interfaces, as it's a WAN router recommended for up dealing with a single DS3.

If you're doing VPN on the router, that will add to the CPU, especially if the router also needs to deal with packet fragmentation.

CiscoNutt · ‎03-12-2015

I am not familiar with DS3, what is it?

The router is acting as a CE router but does not do any inter-VLAN routing, only a gateway to the IPVPN network. And we are running GET VPN on it.

Joseph W. Doherty · ‎03-13-2015

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

It's a serial WAN link that supports 45 Mbps.

3845's are good for about 200 Mbps, or so, of aggregate Ethernet bandwidth. (Again, if your VPN is dealing with fragmentation, CPU consumption, per Mbps, will be higher.)

What the sum of all your ingress (or egress) interface bandwidths when your CPU usage is high?

Ashok Kumar · ‎03-12-2015

Hi,

High CPU due to interrupt, let me give a very brief and concise information-

1. CPU consumed by Interrupt = CPU consumed in packet switching + CPU consumed features configured

2. There's 2 ways to handle the features configured/packet switching, either in the hardware or in software

3. If your device doesn't support the hardware switching/ACL/QoS implementation, more you configure the feature, more high you going to get the CPU

4. Below is the very good guide to troubleshoot the high CPU due to interrupt

http://www.cisco.com/c/en/us/support/docs/routers/7500-series-routers/41120-highcpu-interrupts.html

- Ashok

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CiscoNutt · ‎03-12-2015

Thanks Ashok,

I have already seen this webpage but it did not help much in pinpointing the issue.