How to test Jumbo Frames on a vmkernel port

Here's an "Oldie but a Goodie".  I've been using it recently to sort out some iSCSI issues, so I figured I'd share.

The vmkping command sources a ping from a vmkernel port on the ESXi host.

-I - Allows you to specify a vmkernel port.

-d - Sets the Do Not Fragment bit on the packet.  This MUST be used to test Jumbo Frames.

-s - is the size of the payload.  

From the ESXi shell run the following command:

vmkping -I vmk1 -d -s 8972 x.x.x.x

In my case, I specified vmk1, which is used for the software iSCSI initiator.  x.x.x.x. was my storage array. 

The payload size must be set to 8972 due to the ICMP (8 bytes) and IP (20 bytes) header. .