2651XM router CPU overload

Unanswered Question

I have recently upgraded our corporate internet link to 70Mbps service. I also installed a new screening router that sits between our Bell router and our firewall. When testing the download speed it appears that we cap out at 45Mbps and I notice that the 2651XM CPU hits 90 percent during this download. My feeling is that we are being limited b/c of the router CPU. The router has 256Mb of memory and is running Version 12.4(15)T7. Is this normal for the router CPU to hit 90 percent for 45Mb(bits)ps of thruput ? I do have CEF enabled on the router as I had read that was the best way of route switching packets.

Any help would be appreciated.



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glen.grant Thu, 01/15/2009 - 16:35
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You are probably hitting near the capacity of that router to route packets and thats why the cpu is so high.

Mark Yeates Thu, 01/15/2009 - 18:07
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Glen is correct. That is quite a heavy load for that model of router. Although CEF is configured and running the maximum resources of the router have been reached. A router upgrade is advisable in your situation.

I would say a 2851 or a 3825 would be suitable for your current requirements. If you plan to expand, I would look at a more powerful router.



Joseph W. Doherty Fri, 01/16/2009 - 05:38
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As suggested by the other posters, you likely need a faster router. Cisco, I believe, would recommend a 7200 model once you pass a single T3's bandwidth, although Mark's suggestion of the 2851 or 3825 might suffice. (For 70 Mbps, depending on routine interface load, the 3845 would be another option to obtain even more performance capability.)

Depending on your feature needs, another option might be an "inexpensive" L3 switch, such as a 3560 model.

Attached is a Cisco router performance sheet. Keep in mind you want to allow for duplex forwarding, i.e. 70 Mbps could be 140 Mbps duplex, and you really don't want to "size" a software router, if you can avoid it, pass 50%. (Provides cycles for IOS features and some process switching.) I.e. you might want to consider routers with a CEF Mbps rating of 280 or better. (Again, you could size smaller if the routine link load doesn't max the link.)

glen.grant Fri, 01/16/2009 - 08:27
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I agree if the isp can give you an ethernet interface a layer3 switch would be the way to go.


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