The Oracle VM Server for SPARC virtual switch (vsw) and virtual network (vnet) devices can now support Ethernet frames with payload sizes larger than 1500 bytes. These drivers are therefore now able to increase network throughput.
You enable jumbo frames by specifying the maximum transmission unit (MTU) for the virtual switch device. In such cases, the virtual switch device and all virtual network devices that are bound to the virtual switch device use the specified MTU value.
If the required MTU value for the virtual network device should be less than that supported by the virtual switch, you can specify an MTU value directly on a virtual network device.
In rare circumstances, you might need to use the ldm add-vnet or ldm set-vnet command to specify an MTU value for a virtual network device that differs from the MTU value of the virtual switch. For example, you might change the virtual network device's MTU value if you configure VLANs over a virtual network device and the largest VLAN MTU is less than the MTU value on the virtual switch. A vnet driver that supports jumbo frames might not be required for domains where only the default MTU value is used. However, if the domains have virtual network devices bound to a virtual switch that uses jumbo frames, ensure that the vnet driver supports jumbo frames.
If you use the ldm set-vnet command to specify an mtu value on a virtual network device, future updates to the MTU value of the virtual switch device are not propagated to that virtual network device. To re-enable the virtual network device to obtain the MTU value from the virtual switch device, run the following command:
# ldm set-vnet mtu= vnet-name ldom
Note that enabling jumbo frames for a virtual network device automatically enables jumbo frames for any hybrid I/O resource that is assigned to that virtual network device.
On the control domain, the Logical Domains Manager updates the MTU values that are initiated by the ldm set-vsw and ldm set-vnet commands as delayed reconfiguration operations. To make MTU updates to domains other than the control domain, you must stop a domain prior to running the ldm set-vsw or ldm set-vnet command to modify the MTU value.