Connecting a 2960G to a 1841 router

dnorthrup · ‎06-23-2008

My customer connected a 2960G-48TC-L to a preconfigured C1841 router. The router was hard coded to 10 Full and the 2960G to auto/auto. The 2960G would only auto configure to 10 Half. Hard coding the 2960G to 10 Full knocked down the link as did setting both ports to 100 Full. After several changes the best we could achieve was 100 Full by setting the 2960G to Auto/Auto and the 1841 to Full/Auto. I've unsuccessfully looked though tech notes to see if I could find anything on this specific combination. Has anyone experienced similar issues?

hennigan · ‎06-23-2008

Generally, if either side of a connection is hard-coded, both sides should be. If one end is hard-coded 10 full, it doesn't send FLP so the other side will be at 10 Mbits/s. If hard-coded full duplex, it also won't send duplex negotiation so the other side will default to half.

If you set both sides to auto/auto, you should negotiate to 100-full, which is the best the 1841 is capable of doing.

You could also be able to set both to 100-full and get the same result. However, hard-coding disables MDI-X negotation so the link won't come up if you're using a crossover cable where you shouldn't be or vice-versa.