We've got a Cisco 2811 that experiences periods of extremely high cpu usage. It looks like the problem is CPU inturrupts.
When I run "sho proc cpu sort" it shows the cpu at 98%/84% for instance this morning. However the list of processes total up to less then 25%. Taking a look at the cpu history I can see that sometimes the high cpu usage last for 20-30minutes and sometimes its just a blip for a few minutes. Either way DNS lookups from our web filter take forever and web browsing slows way down.
We have a 10mb WAN link, 100Mb internal link. I can't seem to pin down what exactly is happening but we do some offsite backups (lots of udp traffic) as well as sql replication to a link across town. My guess is that while these backups are running we may be hitting the packet per second limit of the router. I'm also seeing throttles and drops on the interface.
If I take a look at "show interfaces switching" I see the following statistics:
FastEthernet0/0 Internet/WAN
Throttle count 5267
Drops RP 7514 SP 0
SPD Flushes Fast 0 SSE 0
SPD Aggress Fast 0
SPD Priority Inputs 40761680 Drops 0
Protocol IP
Switching path Pkts In Chars In Pkts Out Chars Out
Process 127322510 2383955614 2352954007 3315779514
Cache misses 0 - - -
Fast 271993481 2730636105 1515972958 2966490960
Auton/SSE 0 0 0 0
Protocol DEC MOP
Switching path Pkts In Chars In Pkts Out Chars Out
Process 0 0 34883 2685991
Cache misses 0 - - -
Fast 0 0 0 0
Auton/SSE 0 0 0 0
Protocol ARP
Switching path Pkts In Chars In Pkts Out Chars Out
Process 946716 56802960 855642 51338520
Cache misses 0 - - -
Fast 0 0 0 0
Auton/SSE 0 0 0 0
Protocol Other
Switching path Pkts In Chars In Pkts Out Chars Out
Process 349632 127615230 2097138 125828280
Cache misses 0 - - -
Fast 0 0 0 0
Auton/SSE 0 0 0 0
NOTE: all counts are cumulative and reset only after a reload.
IP inspect is on and we do have a couple of gre tunnels setup on the router also.
Time to upgrade???
