CPU utilization and DRAM !

Unanswered Question
May 8th, 2010
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Hi all.

I have a 3845 router with 256 DRAM and 64 flash. IOS is 12.4(20)T advsecurity. This router is serving as a hub to more then 150+ branches. Firewall is connected to this router and beyond the firwall are 2 internet connections as well.

At peek times, we see the utilization reaching 80-90%, Yesterday i saw it to be at 97%. When i did show processes cpu sorted, the top two processes were

1) IP Input

2) OSPF 100 router

I am confused that when CPU utilization goes high, does it mean that DRAM needs to be upgraded. I mean What is the relation between CPU utilization and DRAM of the router ?

Kindly note that i have cef enabled on all interfaces and globally. I check the router interfaces using show int and dont see any buffer overflow conditions. I do see interfaces dropping the packets. Currently we dont have a support contract and cant open the tac case but i need some urgent help on this. Kindly with your expertise let me know, what shall i do. And also for my confusion, tell me the relation between CPU utilization and DRAM of the router.


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Leo Laohoo Sat, 05/08/2010 - 01:11
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With CEF enabled, the 3845 can push approximately 256mb of un-encrypted traffic.  You said the 3845 is acting as a hub.  How much total bandwidth is your 3845 expected to process?

DRAM is where the IOS gets "expanded".

Jonn cos Sat, 05/08/2010 - 06:05
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Dear Sir,

Can you tell me the possible reasons of high utilization ? i know its a very broad scope but in my assumption, transit traffic should'nt be able to cause it, am i right ?


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