Issue 11
© Solarflare Communications 2014
258
Solarflare Server Adapter
User Guide
Adapter MTU (Maximum Transmission Unit)
The default MTU of 1500 bytes ensures that the adapter is compatible with legacy 10/100Mbps
Ethernet endpoints. However if a larger MTU is used, adapter throughput and CPU utilization can be
improved. CPU utilization is improved because it takes fewer packets to send and receive the same
amount of data. Solarflare adapters support frame sizes up to 9216 bytes (this does not include the
Ethernet preamble or frame-CRC).
Since the MTU should ideally be matched across all endpoints in the same LAN (VLAN), and since the
LAN switch infrastructure must be able to forward such packets, the decision to deploy a larger than
default MTU requires careful consideration. It is recommended that experimentation with MTU be
done in a controlled test environment.
To change the MTU of the vSwitch, from the VMware Console OS enter:
# esxcfg-vswitch --mtu <size> <vSwitch>
To verify the MTU settings, as well as obtaining a list of vSwitches installed on the host, enter:
# esxcfg-vswitch --list
The change in MTU size of the vSwitch will persist across reboots of the VMware ESX host.