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.
Verify that large receive offload and TCP segmentation
offload is enabled on the host.