Operation Jumbo Frames – MTU 9000 for VMware Networking

Wanted to make a quick post about enabling Jumbo Frames in my VMware environment! My switches (Cisco SG-200 & SG-500) support Jumbo Frames so I thought why not? It would surely help push more data through the network for faster for VSAN and vMotions. I’ll do some speed tests later to compare!

Hardware Requirements:

Before you start out on this quest ensure your physical switch support jumbo frames. When enabling it on my Cisco switches a switch reboot was required:

1 Cisco SG Series - Jumbo Frames

The next step is to ensure the NICs in your servers support jumbo frames. If they are server NICs then they should. My Dell T620/R520 both have Broadcom NetXtreme 5709 which in fact support Jumbo Frames.

2 Dell T620 Physical Network Adapters

Enable Jumbo Frames on Virtual Switch:

Now that you confirmed you can physically support Jumbo Frames your ready to enable it in vSphere. If you are using Distributed Switches right click the vDS then Edit Settings:

2 Edit Settings on vDS

On the Properties tab click Advanced. In the Maximum MTU box change it from 1500 to 9000 then click Ok:

3 Operation Jumbo Frame - Maximum MTU

For Standard Switches: Go to vSphere Standard Switch -> Properties -> with vSwitch selected click Edit -> then change MTU to 9000:

2 Edit Settings on Standard Switch

Source: VMware KB 1038828 – Enabled Jumbo Frames on virtual distributed switches

Enable Jumbo Frames on VMKernel:

Now that the switch supports up Jumbo Frames let’s enable it on a vmk virtual adapter. Go to one of your hosts -> Configuration -> Networking -> vSphere Distributed Switch -> Manage Virtual Adapters -> Select a vmk -> Edit:

4 Operation Jumbo Frame - Edit Virtual Adapter

Check if Jumbo Frames are working:

If you have the VSAN health check enabled it does a health check on MTU size:

7 Operation Jumbo Frames - VSAN MTU Health Check

If the computer your on has Jumbo Frames enabled you can also perform a ping test. Open a command window and type:

ping -l 9000 <IP ADDRESS>

8 Operation Jumbo Frames - Jumbo Frame Ping Test

One thought on “Operation Jumbo Frames – MTU 9000 for VMware Networking

  1. Excellent guide. I specifically needed someone to tell me that the MTU 9000 setting needs to go on the virtual switch before that setting goes on the VMK interfaces. I have a switch that supports 10K jumbo frames natively, and I tried setting this up once before on my production vSAN, almost with disastrous consequences because whatever documentation I started from neglected to tell that you can hose your whole network by doing it wrong. Fortunately I was able to reverse the change and put everything back without serious issue.

    I’m still going to check if the rest of my hardware supports jumbo frames before I try to turn it on. But knowing that my physical switch was not the cause of my problem, I’m hopeful that I can get a performance boost thanks to this tip.

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