VMWARE ESXi question MTU with 2008 guest

do you need to change the MTU on the ESXi server and the 2008 guests also , or just the ESXI hosts? ;

or just the 2008 server ?

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Andrew Hancock (VMware vExpert / EE MVE^2)Connect With a Mentor VMware and Virtualization ConsultantCommented:
Not really, Jumbo Frames is only used for storage networks for iSCSI and NFS traffic.

So you would enable it on the VMKernel Portgroup responsible for iSCSI/NFS traffic.

Also you have to ensure, that your

1. physical network switches are configured for jumbo frames.
2. your SAN or NAS is also configured for jumbo frames.
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Chaging the MTU size, because you want to use Jumbo Frames, needs to be set on the network interface, that will benefit from using jumbo frames, e.g. storage network for iSCSI or NFS.

So if you will be using iSCSI and NFS traffic on your network interfaces on the Host ESXi Server e.g. VMKernel Portgroup and inside the Windows 2008 VM.

Then you will need to set MTU (e.g. 9000) on both VM Guest and ESXi Host.

if you do not use NFS or iSCSI (e.g. Microsoft iSCSI Initiator) in the VM, then MTU size increase is not required.

Why do you need to change MTU?

see my EE Article

HOW TO: Enable Jumbo Frames on a VMware vSphere Hypervisor (ESXi 5.0) host server using the VMware vSphere Client
NAMEWITHELD12Author Commented:
Actually I need to lower it to about 1200 or so.

do you know what the ESXCFG command is to check this or set this via the command line

if you set  the MTU on the Host and the Guest VM to 1200 would this be ok?

could I set it just on the switch and the host ?

for best practices where should the MTU be set at ?

thanks !
NAMEWITHELD12Author Commented:
Configuring ESXi
Support for jumbo frames has been included in ESX and ESXi for quite a while. But up until version 5.0 of vSphere is was not exposed in the GUI for both the default vSwitch and Distributed vSwitch implementation. It had to be configured via the ESX CLI for a default vSwitch and VMkernel port. Since vSphere 5.1 it is possible to configure the MTU settings via the GUI for all three elements.

THis seems to indicate that you would want to set the MTU at all 3 locations vSwitch, Kernal port and the ESXi host ? is this right ?

Dont get into complications Keep the same MTU on the Physical Switch and VSwitch The simpler the environment the best it is
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