Is it possible to oversubscribe an Ethernet interface?

[daniel.bowen]

I have a 7513 router with four 10BaseT Ethernet interfaces, four 100BaseTX interfaces and two ATM interfaces. We have an independant company connected to interface E8/0/4 and they seem to be oversubscribing the interface. The problem is, that at certain times the interface is showing 2500 - 3000 packets input, with 9325872 output drops. This causes the routers CPU to shoot through the roof, causing EIGRP recalcs etc. As soon as I shut down this interface the problem goes away (within 1 second).

Could this interface be sending so much traffic that it is killing the CPU, and is there anything I could do about it?

Thanks in advance,

Daniel,

[ttuncaral]

I would suggest you to check cable connection first. And then, check port configurations on both sides (router and -if exist switch/hub). Sometimes AUTO negotiation option may cause Ethernet errors.

Could you check SHOW PROC CPU output in oder to find which process causes high CPU?

[bbranch]

If the return traffic flow is from the ATM or Fast Ethernet to the 10Mb Ethernet then you may be oversubscribing the Ethernet link, this can then cause output drops and possibly receive side buffering which in turn can slow the box down.

There's a good URL on CCO covering these topics which may be of some use identifying the cause:

http://www.cisco.com/warp/public/63/queue_drops.html

http://www.cisco.com/warp/public/63/vip_cpu_rxbuffering.html