6.5.1

Table Of Contents
LRO reassembles incoming network packets into larger buffers and transfers the resulting larger but
fewer packets to the network stack of the host or virtual machine. The CPU has to process fewer packets
than when LRO is disabled, which reduces its utilization for networking especially in the case of
connections that have high bandwidth.
To benefit from the performance improvement of LRO, enable LRO along the data path on an ESXi host
including VMkernel and guest operating system. By default, LRO is enabled in the VMkernel and in the
VMXNET3 virtual machine adapters.
For information about the location of TCP packet aggregation in the data path, see VMware Knowledge
Base article Understanding TCP Segmentation Offload (TSO) and Large Receive Offload (LRO) in a
VMware environment.
Enable Hardware LRO for All VMXNET3 Adapters on an ESXi Host
Enable the hardware capabilities of host physical adapters to aggregate incoming TCP packets for
VXMNET3 VM adapters by using the LRO technology instead of consuming resources for assembling in
the guest operating system.
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.Vmxnet3HwLRO parameter.
n
To enable hardware LRO, set Net.Vmxnet3HwLRO to 1.
n
To disable hardware LRO, set Net.Vmxnet3HwLRO to 0.
5 Click OK to apply the changes.
Enable or Disable Software LRO for All VMXNET3 Adapters on an
ESXi Host
Use software LRO in the VMkernel backend of VMXNET3 adapters to improve networking performance of
virtual machines if the host physical adapters do not support hardware LRO.
vSphere 5.5 and later supports software LRO for both IPv4 and IPv6 packets.
Prerequisites
Procedure
1 In the vSphere Web Client, navigate to the host.
2 On the Configure tab, expand System.
3 Click Advanced System Settings.
vSphere Networking
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