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New Member

High CPU Utilization on IOS VPN router

Dear all,

I have a cisco7206 with NSE1 and VAM installed, running in IOS12.2.15T2, is configured for the window l2tp/ipsec vpn connection. I can successfully establish the l2tp/ipsec connection from my WinXp to the router. However, I found that the CPU utilizaton is increased around 50% to 60% once I transferring the data through the tunnel.

In the output of sh proce cpu, the high cpu utilization is in "IP Input" process.

In the output of "sh int stat", all the traffic are being process switched in the virtrual access interface.

Both CEF and flow switching are already enabled at all interfaces, and the virtual template is also defined the MTU size 1000 to avoid fragmentation in l2tp tunnel. Does anyone have the same problem, and advise how can I fix the high cpu utilization problem.



Re: High CPU Utilization on IOS VPN router

I had the same issue, it was down to the IOS. It needs to be an `E' train IOS image. I used 12.1.9(E) which fixed problem.

If you do a show ver, does the `integrated service adapter' appear under the installed hardware, if not then its your IOS.


New Member

Re: High CPU Utilization on IOS VPN router

Hi Andy,

Thanks for your reply. Yes, it may be the IOS problem. I noticed that the virtual access interface was turned off all switching methods when my win98 connected to router. After searched the cisco bug toolket, it is very similar to the symptom of bug cscdw57010.

The high cpu utilization in IP input is gone after added the comand "vpdn ip udp ignore checksum" into the router configuration.


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