As I understand how Ethernet negotiation works, there will always be a loss of connectivity.

Lets say your PC and it's switch have auto-negotiated a 100/full duplex connection and you change your PC's connection to 10/half. The switch then realizes that it can no longer reach your PC at 100/Full and begins a new auto-negotiation cycle. When it finds your NIC at 10/half it will connect again at that speed/duplex.

In theory you could manually configure both devices at once, but I have no idea how to do so in practice. And I bet there still would be a period of non-connectedness.

You are not just changing the speed at one end, both ends need to be in sync.

I tried to remain child-like, all I achieved was childish.

Tsar of all the Rushers

BTW, you can never manually configure just one end to a full duplex setting. You must configure both ends or let the entire configuration be automatic to use Full Duplex.

http://arstechnica.com/civis/viewtopic.php?p=16053...

I tried to remain child-like, all I achieved was childish.

Tsar of all the Rushers

If you change the duplex setting on an interface, the interface it is facing will continue to operate in whatever duplex mode it was already in until next time it is reset.

If you change the speed, that resets the interface, so it renegotiates on the way back up.

For example, you have 2 facing interfaces, both set to auto/auto. They have autonegotiated 100/Full.

- If you change one end to 100/Full instead of Auto/auto, both will remain on 100/Full. Next time you reset the interface, the one set to auto/auto will fail to negotiate and autodetect the speed as 100 and set the duplex to whatever the default value is - usually 100/Half (stupidly).