Monday, October 31, 2011

Set higher MTU for vSwitch and Virtual Distributed Switch

 Refer to KB: iSCSI and Jumbo Frames configuration on ESX 3.x and ESX 4.x for more details

**Any packet larger than 1500 MTU is a Jumbo Frame. ESX supports frames up to 9Kb (9000 Bytes).

 To set the MTU size for the vSwitch, run the command:

# esxcfg-vswitch -m (MTU_Number) (Vswitch)

where MTU_Number = 9000, Vswitch = Name of the Vswitch

This command sets the MTU for all uplinks on that vSwitch. Set the MTU size to the largest MTU size among all the virtual network adapters connected to the vSwitch.

Refer to KB: Enabling Jumbo Frames for VMkernel ports in a virtual distributed switch

Run this command to change the MTU size for the individual port group:

# esxcfg-vmknic -m 9000 -v (port number) -s (dvs Switch name) 

For Example:
# esxcfg-vmknic -m 9000 -v 115 -s "NewLAN-DVS"

To enable Jumbo Frames on a VMkernel port from vCenter Server:

1) Click Home > Hosts and Clusters > Host > Configuration > Networking.
2) Navigate to the vSphere Distributed Switch tab.
3) Click the VMkernel port (eg: vmk1)
4) Click Manage Virtual Adapters.
5) Select the vmk interface and click Edit.
6) Under the NIC settings, change the MTU value to 9000.
7) Click OK.

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