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After upgrade from 2821 to 3845 Cisco Router CPU Usage 98% & memory drops until it crashes.

Posted on 2008-11-06
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Last Modified: 2012-05-05
Hello,
I have recently attempted to migrate a 2821 Cisco Router to a 3845.  I copied the configuration over letter for letter.  When we installed the router everything looked fine so I setup NBAR.  CPU usage was simi high but that was to be expected I thought with nbar.  After about an hour of playing with it I saw the memory was dropping consistently so I turned off nbar but it was still dropping.  Then once it reached about 15% free memory I reloaded it.  Now CPU usage was higher then when NBAR was on and memory was dropping twice as fast.  Rebooted again before it crashed and CPU usage was so high the CLI became unresponsive until it crashed and still was losing memory consistently.  Tried again today and saw most of the CPU is being used by IP NAT AGER.  Owner got nervous and had me move things back before I could get much more information.  Any Ideas?  Here is my config:

23883941-config.txt
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Question by:bobertperry
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by:JFrederick29
ID: 22907592
I would upgrade the code since you may be running into a bug with the current IOS you are running.  Are you running the same IOS as the 2800?
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Author Comment

by:bobertperry
ID: 22907740
That is what I thought too so I tried downgrading the IOS from 12.4(22)T to 12.4(16)T but still had the same problem.  The 2800 is running 12.3.  We do need an IOS newer then 12.4(4) but I will back rev it to the same spot as the 2800 and let you know in a few hours.
rp
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JFrederick29 earned 2000 total points
ID: 22907947
Little bit of cleanup, not to say this is the problem but, you can combine your subnets into a single access-list so you only have one "ip nat inside source list" command:

i.e.

ip access-list standard 90
permit 10.149.0.0 0.0.1.255
permit 10.100.0.0 0.0.0.255
permit 10.151.0.0 0.0.1.255
permit 10.152.0.0 0.0.1.255
permit 10.153.0.0 0.0.1.255
permit 10.102.0.0 0.0.1.255
permit 10.154.0.0 0.0.1.255
permit 10.155.0.0 0.0.1.255
permit 10.103.0.0 0.0.1.255
permit 10.156.0.0 0.0.1.255
etc...

ip nat inside source list 90 pool XXXX-slash-22

You can then remove the other "NAT access-lists" (2-44, 98, 99) and the other "ip nat inside source list" commands.

This will make things more efficient but again, I'm sure you are running into a bug if you had this same exact config on the 2821 without issue.
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Author Comment

by:bobertperry
ID: 22909185
You are sexy.  Thank you.
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