I recently upgraded my 100Mbps switch to a Gigabit switch. However, I noticed that the ESXi NICs are still running at 100 Mbps, not 1000Mbps. So using vSphere Client I changed the speed to 1000Mbps, and oh boy what a disaster that was. That seemed to trash the network connection which meant everything stopped working and I could no longer connect to the ESXi host though vSphere Client. And because I couldn't connect with vSphere Client I couldn't change the speed back to 100Mbps. So I ended up going into the ESXi console and choosing Reset from the menu which essentially means starting again with a blank ESXi config. This was of course very frustrating.
So my questions are:
1) Why might the NICs be running at only 100Mbps even though they're now connected to a Gigabit switch?
2) How do I get them running at Gigabit without losing network connectivity?
3) If I do run into the same problem again, how can I reset the NIC without having to do a complete ESXi reset?