Enabling jumbo frames support on appropriate components

The original IEEE 802.3 specifications defined a valid Ethernet frame size from 64 to 1,518 bytes. Considering that the standard Ethernet header is 18 bytes in length, then the payload for a standard frame ranges in size from 46 to 1,500 bytes. This is the Maximum Transmission Unit (MTU).

Jumbo frames are Ethernet frames with more than 1,500 bytes of payload, typically around 9,000 bytes. Note that ESXi supports 9,000 bytes a maximum frame size, which you can configure.

You must enable jumbo frames end to end, so there are many places where you have to set the right MTU: physical switches, virtual switches, end interfaces (vNIC and VMkernel adapters). Otherwise, the performance will not increase, but rather do the opposite due to packet fragmentation.

You can enable jumbo frames both on a vSphere Distributed Switch and a vSphere standard switch by changing the MTU to a value greater than 1,500 bytes. For a vDS, just go into the Advanced menu in the vDS settings:

Where should you enable jumbo frames? Usually, they are mostly used for IP-based storage traffic. If you plan to use jumbo frames for iSCSI or NFS traffic, see KB 1007654 (https://kb.vmware.com/s/article/1007654)—iSCSI and Jumbo Frames configuration on VMware ESXi/ESX.

For more information, see the vSphere 6.5 Networking guide (https://docs.vmware.com/en/VMware-vSphere/6.5/com.vmware.vsphere.networking.doc/GUID-53F968D9-2F91-41DA-B7B2-48394D997F2A.html).