Jumbo Frames – Do It Right

Configuring jumbo frames can be such a pain if it doesn’t get done properly. Over the last couple of years, I have seen many customers having mismatched MTUs due to improperly configured jumbo frames.. If it is done properly, jumbo frames can increase the overall network performance between your hosts and your storage array. It is recommendable to use it if you have 10GbE connection to your storage device. However, if it is not configured properly, jumbo frames quickly become your worst nightmare. I have seen it causing performance issues, drops of connection as well as ESXi hosts losing storage devices.

Now, we all know what kind of issues jumbo frames can cause as well as it is advisable to use it if you have a 10GbE connection to your storage device. However, let’s discuss some details about jumbo frames:

  • Larger than 1500 bytes
  • Many devices support up to 9216 bytes
    • Refer to your switch manual for the proper setting
  • Most people will refer to jumbo frame as a MTU 9000 bytes
  • It often causes a MTU mismatch due to misconfiguration

 

Below’s steps offer guidance on how to setup jumbo frame properly:

Note: I recommend to schedule a maintenance window for this change!

On your Cisco Switch:

Please take a look at this Cisco page which lists the syntax for most of their switches.
Once the switch ports have been configured properly, we can go ahead and change the networking settings on the storage device.

On Nimble OS 1.4.x:

  1. Go to Manage -> Array -> Edit Network Addresses
  2. Change the MTU of your data interfaces from 1500 to jumbo

nimble_1-4-X_jumbo

On Nimble OS 2.x:

  1. Go to Administration -> Network Configuration -> Active Settings -> Subnets
  2. Select your data subnet and click on edit. Change the MTU of your data interfaces from 1500 to jumbo.

NimbleOS2X_jumbo

 

On ESXi 5.x:

  1. Connect to your vCenter using the vSphere Client
  2. Go to Home -> Inventory -> Hosts and Clusters
  3. Select your ESXi host and click on Configuration -> NetworkingESXi_networking
  4. Click on Properties of the vSwitch which you want to configure for jumbo framesvSwitch_properties
  5. Select the vSwitch and click on Edit.
  6. Under “Advanced Properties”, change the MTU from 1500 to 9000 and click ok.vSwitch_Jumbo
  7. Next, select your vmkernel port and click on Edit.
  8. Under “NIC settings” you can change the MTU to 9000.vmk_jumbo
  9. Follow step 7 & 8 for all your vmkernel ports within this vSwitch.

After you changed the settings on your storage device, switch and ESXi host, log in to your ESXi host via SSH and run the following command to verify that jumbo frames are working from end to end:

vmkping -d -s 8972 -I vmkport_with_MTU_9000 storage_data_ip

If the ping succeeds, you’ve configured jumbo frames correctly.

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