I am facing a weird problem in 7206VXR-NPEG1 router. The router has a STM1 interface to WAN facing side and onboard gigi interfaces on LAN side.
CPU of the router goes only high during peak production hours. CPU is constanly in 70% and maximum CPU goes till 92% when the traffic of STM1 is around 50-55Mbps and above. When the traffic of STM1 drops below 40Mbps then CPU also drops down to 50% and during night time when the traffic of STM1 drops around 20Mbps then CPU comes down to 20-30%. It infers the CPU is heavily based on the traffic flowing through it and not on any specific protocols or processes, it is only due to interrupts.
show process cpu shows most of the CPU is due to the interrupt and no single process is holding high CPU. Of course I could see BGP (scanner and event) and OSPF is showing as top contributor (around 4%) of CPU to the total 80% which I think is very negligible. The IOS that I have has BGP Next Hop tracking feature enabled so CPU due to BGP scanner is not an issue.
I also made sure that CEF is enabled and all the points discussed in this doc: http://www1.cisco.com/en/US/products/hw/routers/ps359/products_tech_note09186a00801c2af0.shtml#pxf_punts but still of no help to me.
Can somebody point me what would be my next step in finding out the root cause of the issue.
Is CPU Profiling the way now for me to find out the root cause due to interrupts?
Is this could be related to the STM1 interface on hardware. (though it sounds weird, i am thinking of all possibilities).
any help is much appreciated...