You can check whether TSO is enabled on a particular VMkernel networking interface.

1

Log in to your ESX host's console.

2

Use the esxcfg-vmknic -l command to display a list of VMkernel interfaces.

The list shows each TSO-enabled VMkernel interface with TSO MSS set to 65535.

If TSO is not enabled for a particular VMkernel interface, the only way to enable it is to delete the VMkernel interface and recreate the interface.