Enable or Disable TSO on an ESXi Host

Enable TCP Segmentation Offload (TSO) on the transmission path to have the NIC divide larger data chunks into TCP segments. Disable TSO to have CPU perform TCP segmentation.

By default, a host uses hardware TSO if its physical adapters support it.

Procedure

1. In the vSphere Web Client, navigate to the host.
2. On the Configure tab, expand System.
3. Click Advanced System Settings.
4. Edit the value of the Net.UseHwTSO parameter for IPv4 and of Net.UseHwTSO6 for IPv6.
   • To enable TSO, set Net.UseHwTSO and Net.UseHwTSO6 to 1.
   • To disable TSO, set Net.UseHwTSO and Net.UseHwTSO6 to 0.
5. Click OK to apply the changes.
6. To reload the driver module of the physical adapter, run the esxcli system module set console command in the ESXi Shell on the host.
   1. To disable the driver, run the esxcli system module set command with the --enabled false option.

      esxcli	system module set	--enabled false --module nic_driver_module

   2. To enable the driver, run the esxcli system module set command with the --enabled true option.

      esxcli	system module set	--enabled true --module nic_driver_module

Results

If a physical adapter does not support hardware TSO, the VMkernel segments large TCP packets coming from the guest operating system and sends them to the adapter.