ESXi 4.1 and NIC speeds

jfish · 16 Oct 2012 at 13:38

I have an ESXI server with 2 nics connected

one is 100 mb and the other is 1 gb

Windows 2008 R2 is showing the NIC speed as 10 GB - which I suspect is false information from Windows.

will ESXi use the lowest speed for the network . even setting one NIC at 1 GB and due to the other being 100 MB it will automatically downgrade to 100 MB

RSR · 16 Oct 2012 at 14:21

ESX / ESXi will use physical link speed.

jfish · 16 Oct 2012 at 14:25

[RXP]Andy;22971513 said:
ESX / ESXi will use physical link speed.

so it doesnt matter if one NIC is set to 100 whilst the other is set to 1Gb - it wont dowgrade the link speed then.

RSR · 16 Oct 2012 at 14:32

jfish said:
so it doesnt matter if one NIC is set to 100 whilst the other is set to 1Gb - it wont dowgrade the link speed then.

It depends how its been setup, if the VM's are on this same host they will communicate at bus speed and if the VM is connected to a vSwitch or vDS they will communicate at the speed the physical adapter is connected it.

mole90 · 18 Oct 2012 at 20:01

jfish said:
so it doesnt matter if one NIC is set to 100 whilst the other is set to 1Gb - it wont dowgrade the link speed then.

Its not really good to mix NICs connected at different speeds to the same vSwitch, but if you do, ensure that the lowest speed one is set as standby.

VMs with the vmxnet3 NICs on the same host will be able to communicate with each other at 10Gbps (faster if any of the software supports VMCI) but traffic leaving the vSwitch to the external network will be at 1Gbps.

ASE001 · 18 Oct 2012 at 20:18

ESX present a virtual NIC to the guest operating system which defaults to 10Gbit.