Enable Large Receive Offload

Large receive offload (LRO) is a technique for increasing the inbound throughput on high-bandwidth network connections by decreasing CPU overhead. Without LRO, the firewall drops packets larger than the configured maximum transmission unit MTU, which is a maximum of 9216 bytes when the firewall is enabled for jumbo frames. With LRO enabled, the firewall accepts packets up to 64KB in size and the does not drop packets larger than the configured MTU. Instead, it segments the larger packets into smaller chunks of 9000 bytes. For example, if the VM1 sends a 64KB packet to VM2 and the packet is divided into eight segments.
LRO is disabled by default on new NSX-V deployments and upon upgrade. You can enable or disable LRO and view the LRO status on through the CLI. Enabling LRO on the VM-Series firewall automatically enables jumbo frames. Additionally, LRO and TCP Segmentation Offload (TSO) must be enabled on VMXNET3 network adapter on the VM-Series firewall host machine.
  1. Verify that large receive offload and TCP segmentation offload is enabled on the host.
    For information about LRO and TSO on the host machine, see theVMware vSphere documentation.
    1. Log in to vSphere and navigate to your host machine.
    2. Select
      Advanced System Settings.
    3. Locate the following parameters and verify that their value is set 1. A 1 indicates that the parameter is enabled on the VMXNET3 adapter.
      • For LRO—Net.Vmxnet3HwLRO
      • For TSO—Net.UseHwTSO and Net.UseHwTSO6
  2. Enable LRO on the VM-Series firewall.
    1. Use the following command to enable LRO:
      set system setting lro enable
    2. Reboot the firewall using the following command:
      request restart system
    3. Verify the LRO is enabled with the following command:
      show system setting lro
      Device LRO mode: on Current device mtu size: 9192
      You can disable LRO using the command
      set system setting lro disable

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