This is a rather interresting problem I ran into at WORK, and I was wondering if anyone KNEW why this was happening...

An old 10/100 switch was dying due to a cooling fan squeeling loudly. I swapped this switch out with a 10/100/1000 Netgear Smart Managed Switch and two servers started having problems keeping their link light. The SYSTEMS would be online then go offline and back online as the link led would STAY solid then go out, then stay solid again.

Replacing the 3com905B-TX Fast Etherlink XL PCI NIC on the exchange server with a brand new 1000mbps Linksys NIC fixed the exchange server. But then the active directory server started to have the same problem soon after ( about 2 hrs after ). All other 10 and 100mbps hardware connected to this new switch was running fine the whole time after the upgrade/ replacement of the switch.

I ended up moving the network cable from jack 16 on the gigabit switch to 16 which was also available on the older 10/100 switch above it which had an available port and the link for the network adapter would then stay solid and the problem was resolved.

Has anyone seen problems like this where the older 10/100 NICs misbehave on newer 10/100/1000 switches which should be backwards compatible?

The active directory server also had the same 3com905B-TX Fast Etherlink XL PCI NIC installed which was rather interresting since this NIC make/model and the new switch seem to have a handshake issue.

Thanks,

DaveWhat is happening is that the machine with the NIC acting up is trying to set a good speed in which to connect to the switch. A lot of times with newer NICs or switches the 1000 speed is what creates the problem. The NIC on your machine is set to auto so it keeps trying to change the speed setting to sync up with the switch but the switch can go a lot faster than the NIC so they never really sync up.

To fix this login to the machine that is not working and change the speed setting for the NIC to 100 full-duplex or some other speed. Just be sure it is not on auto.

Right click the NIC-->properties-->configure-->Advance-->Media TYPE

Than look at the drop down to change the settings