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1841 at 99% CPU what can I do?

Andy White


I've never had a router's CPU suddenly hit 99% and just stay like it for hours even after a reboot.  This router really does nothing with regards to CPU, I'm looking at it's CPU history (via SolarWinds Orion NPM software that we use) and it is arounf 1-3% all the time for the past 2 years.

What commands can I use to diagnose the issue?

I did a show debugigng and it seems no debugging is running


9 Replies 9

Sandeep Choudhary
VIP Mentor VIP Mentor
VIP Mentor

Can you paste the output of this command;:

show processes cpu

see this link:


Please rate if it helps.

Peter Paluch
Hall of Fame Cisco Employee Hall of Fame Cisco Employee
Hall of Fame Cisco Employee

Hi Andy,

Can you see the output of the show process cpu sorted 1m and post it here? This output should tell you the processes whose 1-minute CPU load average is the highest. This should eventually help us see what process consumes the most of your CPU power.

Best regards,


Thanks guys, it's

97.37%    IP NAT Ager

The routers main purpose is to NAT to be honest.

Hi Andy,

To find out the root cause you can enable netflow in your local lan  interface and find out whats happening with the traffic transactions.

With that you can come to a solid conclusion or atleast get a clue on what is making or hogging the CPU up.

Configure ip route-cache flow under your local lan ethernet interface and make use of show ip cache flow to check the traffic transactions.

Hope the below link helps u out.

may be its a Buggy IOS, upgrade.?


Please rate if it helps.

Maybe a bug, Neflow is already running and shows hardly any traffic.

Memory is up from 20% to 80% too.

Hello Andy

Can you give a     clear ip nat translation *     and see whether the CPU comes down.. and what is the traffic on the outgoin interface show interface < interface name>



Hi, I've already clear the table and it still stays at 99%

IOS is old, had a look a newer IOS but there are so many to choose, I'd appreciate if you can help locate a newer one?  Form the below output it would seem that the memory is 128mb and flash 32mb, I tried to see if this current IOS has been deferred but it wasn't listed.

Compiled Fri 30-Nov-07 14:10 by prod_rel_team

ROM: System Bootstrap, Version 12.3(8r)T8, RELEASE SOFTWARE (fc1)

NAT_router uptime is 3 hours, 23 minutes

System returned to ROM by power-on

System restarted at 11:14:50 bst Mon Oct 8 2012

System image file is "flash:c1841-ipbasek9-mz.124-18.bin"

Cisco 1841 (revision 5.0) with 114688K/16384K bytes of memory.

Processor board ID FCZ092822QY

2 FastEthernet interfaces

DRAM configuration is 64 bits wide with parity disabled.

191K bytes of NVRAM.

31744K bytes of ATA CompactFlash (Read/Write)

Hi Andy,

See this link:
Chosse what services you want on router and  decide which IOS u can take.


Please rate if it helps.

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