Unexpected behavior when autonegotiation fails

unnamedplayerunnamedplayer Posts: 74Member ■■□□□□□□□□
Hello all,

Working on CCENT/CCNA using Odom's book and I am trying to demonstrate autonegotiation and duplex mismatches.

According to Odom, when autonegotiation fails, for example when it is turned off on one end of the link, the switch should still be able to sense the speed, but it will choose the duplex based on the speed: half duplex for 10/100 and full for 1000.

I have 2 switches, a 3550 and a 2960 connected via a trunk port. I turned off autoneg on the 2960 by hardcoding speed 100 and duplex full, and the 3550 behaved as expected. It picked up the 100Mb speed and set the duplex to half.

However, when autoneg is off on the 3550 and on on the 2960, the 2960 detects not only the speed, but the duplex as well! For example, on the 3550, I set speed 10, duplex full, and the 2960 shows its interface as being 10/full as well.

Can someone explain to me what is going on? Is this a new feature on the 2960 that it can find the duplex from some other means? Thanks for the help!
Sign In or Register to comment.