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CPUHOG: IP NAT AGER

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andrew4728

Technical User
Joined
Jul 6, 2004
Messages
61
Location
US
Hey all, I have been troubleshooting this for a while now, and I'm starting to think perhaps my router (Cisco 2514 16 meg, 12.2 IOS) just can't fully handle what I am using it for.. Shrug. This is for home use, not corporate BTW. (mainly educational)

my problem is IP NAT AGER process is taking up a large amount of CPU, and at times causing my router to stop processing packets for several seconds. As I'm sure you are aware, this can jack up my gaming!!! not acceptable!

This is one example :
Oct 21 11:55:28: %SYS-3-CPUHOG: Task ran for 2916 msec (11/7), process = IP NAT Ager, PC = 37CBDCE. -Traceback= 3225BA8 37CBDD6

Now, I'm quite sure I know the root cause of this problem: P2P program I am running. The program generates anywhere from 2500 to 4000 NAT translations. This is overloaded through my single IP via cable modem.

I am trying to find a way to configure the router to work with this situation, rather than stop using the P2P. Also, I have been playing with a second P2P on my Girlfriends computer to see if that made situation worse or not. It did bump nat translations up to 7000+, but the IP NAT AGER process seemed to spike the cpu about the same amount.

My main question is, does anyone know if there is a specific limit on IP NAT TRANSLATIONS the 2500 series can handle overloaded?

I have attempted to leave the nat timeouts to default settings, have also set the following that I found suggested on some websites :

ip nat translation timeout 3600
ip nat translation tcp-timeout 3600
ip nat translation udp-timeout 3600

I even set timeouts to 60 seconds to see if that would help keep the trans table clear, but that started to affect some connectivity with such short timeouts..

Does anyone know if this IP NAT AGER program runs at specific intervals? or is constantly keeping an eye on the age of ip nat entries and clearing them off at the specified timeouts?

I've searched the web for months now, and havn't been able to find anything useful, except one page that is in asian which I can't read.. The info on the page that I CAN read appears to show that the page is related to my exact problem, but I can't read it dag nabit :(

Thank you for any help/suggestions you have!


 
Oh, also a side note :
This high amounts of NAT translations is not due to a virus or a worm or any such thing,, mostly generated by P2P software..
If I disable the P2P's and give it aprox an hour or so, the translation table clears down to a low 30ish...
 
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