Is there a command to test whether jumbo frames are actually working? i.e. some sort of "ping" that reports whether or not the packet was broken up along the way.

I've an ESXi host with an Ubuntu VM which mounts a Dell MD3000i via iSCSI. I suspect jumbo frames are not enabled on the switch, and can't easily get admin access to it. I have the option to connect the disk array directly to the ESXi host, but would like some way of confirming that jumbo frames are a problem first.