with a payload of 15000 bytes…) without showing an error.Īs we do not want this behaviour for our tests we can use the parameter -d, which will disable IP fragmentation. This is the reason why every payload size will work (try it e.g. When the Internet Protocol has to send a packet larger than its frame, it will divide the message into fragments for transmission by design. Now you know that you should use the command “vmkping -s 8972 IP-address” to test your infrastructure when using a MTU size from 9000 bytes.īut there is one thing more to take care.

The size you need to use in your command will be:ĩ000 (MTU size) – 8 (ICMP header) – 20 (IP header) = 8972 bytes for ICMP payload This happens because ICMP needs 8 bytes for its ICMP header and 20 bytes for its IP header: 9000 bytes and use this size in your vmkping command, you may get a “Message too long” error. With the parameter -s you can define the size of the ICMP payload. How to use vmkping right when testing Jumbo Frames?Īssuming you have configured everything right, you will now use vmkping to verify if everything is working as expected.īut the vmkping command has some parameters you should know and use in this case: – now you can change the MTU size in the section “Advanced Properties”: – open “Properties” from your vSwitch and click “edit” – open the “Configuration tab” and select “Networking” – open your vSphere Client and select a Host. It is very easy to change the MTU size on your vSwitch: How to enable Jumbo Frames on your vSwitch? your network must support Jumbo Frames end to end.Jumbo Frames are limited to data networking only (vMotion & virtual machines network).maximum MTU size supported by ESXi is 9000 bytes.In most cases, you would configure the MTU to a jumbo frame size, which is 9000. vMotion, Storage: NFS, iSCSI and VSAN are examples that would gain some performance by increasing the frame size. every MTU size larger 1500 bytes is a Jumbo Frame Several vSphere components can benefit from using a larger network frame size (MTU) than the regular size of 1500 bytes.But you should take care how to use this command. You have configured Jumbo Frames in your VMware infrastructure and want to verify if everything is working well? No problem – you can do this with the command vmkping.

Vsphere mtu 9000