Changing NIC Duplex

[msc7808]

I just installed ESXi on the new hardware. The motherboard (Intel BOXDG45ID )has Gigabit NIC on board. While reviewing the settings in VC i changed the NIC to 1000 MBPS Full Duplex from 100 MB Full Duplex. As sooon as I did it, the VC lost connection to the host. Could'nt ping the box.

Tried restarting the Management Services and it didn't work. Had to restore the settings from the console.

Could someone please explain why this happened and what is the procedure for troubleshoot this sort of scenario?

Thanks

Manny

[casselc]

You most likely created a duplex mismatch between the NIC and the switchport it's attached to. If the port was initially showing 100/Full in the VI client then it's probably attached to a 100Mb auto-negotiating port; forcing the host's NIC to 1000/Full would interfere with auto-negotiation and leave both sides operating at different speeds and duplex settings. Generally duplex mismatches will leave the connection operational but very slow.

As for troubleshooting, the switchport will generally show a lot of errors and collisions and I've noticed on Cisco switches that the port will usually be listed at auto-10/auto-half or auto-100/auto-half. In general I try to be certain of the speed and auto-negotiate settings of any ports I attach to, and only change the default NIC settings if I know the switchport is manually configured for a certain speed/duplex.

[msc7808]

THANKS. MINE IS CONNECTED TO LINKSYS ROUTER PART OF MY HOME LAB. I THOUGHT OF THE SAME EARLIER HOWEVER COULDNT FIND SETTINGS IN THE ROUTER TO TWEAK.

IS IT NOT POSSIBLE TO REVERT THE NIC SETTINGS USING THE TECH SUPPORT MODE COMMAND LINE AT THE CONSOLE?

[casselc]

You can set a NIC back to autonegotiate from the command line using esxcfg-nics -a vmnic0 or whatever the vmnic# happens to be.

[msc7808]

Perfect. Thanks for your help.

[msc7808]

it worked. thank you