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MTU in vSphere Environment


Understanding on VMware Jumbo Frames - MTU

In VMware, it represent the transmission unit over network. In simple words, jumbo frames are ethernet frame with payload greater than the standard maximum transmission unit (MTU) 1500 bytes. It allow Esxi to send larger frames into physical network which not only increase the network throughput also cut down CPU utilization while in of using ISCSI storage.


Let's look at it more on their implementation & limitations.

  • Packet larger than 1500 MTU is a Jumbo Frame. ESX/ESXi supports frames up to 9000 Bytes.

  • It can be configure for an iSCSI network however It is not a supported configuration in ESXi/ESX 3.5, but it is supported in later versions e.g ESXi/ESX 4.x, ESXi 5.x and 6.0. (For 5 and later version, it can be configure through GUI also)

  • You can enable Jumbo Frames for each vSwitch or VMkernel interface through the command line interface on your ESX host however the network must support Jumbo Frames end to end.

  • Ensure that your NIC or LOM supports Jumbo Frames.

Configuring Jumbo Frames on a vSphere Standard Switch

  1. Log in to the vSphere Client.

  2. Select the Hosts and Clusters inventory view.

  3. Under the host Configuration tab, click Networking.

  4. Click Properties for the vSphere standard switch associated with the VMkernel to modify.

  5. Under the Ports tab, select the VMkernel interface.

  6. Click Edit.

  7. Set the MTU parameter to 9000.

  8. Click OK.

Enabling Jumbo Frames for all VDS

To configure Jumbo Frames on a vDS in vSphere Web Client for vCenter Server 5.1, vCenter Server 5.5 and vCenter Server 6.0:

  1. Browse to a distributed switch in the vSphere Web Client navigator.

  2. Click the Manage tab, and click Settings > Properties.

  3. Click Edit.

  4. Click Advanced and set the MTU property to a value greater than 1500 bytes.

  5. Click ok

​Notes:

  • You cannot set the MTU size to a value greater than 9000 bytes.

  • When changing the MTU size in a vDS, the attached uplinks (physical NICs) are brought down and up again. This causes a short (less than 5 to 10ms) network outage for virtual machines and/or services that are using the uplinks.

Open a case with hardware vendor to understand support functionalities of network interface card with jumbo frames.

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