Advanced Speed Troubleshooting- MTU

Ruth Petty -

For optimal VPN speeds, one common adjustment is MTU or Maximum Transmission Unit. Adjusting this setting on your computer, VPN Router or OpenVPN script, allows more bytes of data through that protocol layer. While this may seem intimidating, the basic troubleshooting for MTU is relatively simple.

Finding your Settings


Visit to determine what defaults your MTU and MSS are set at. If your MTU is less than 1500 see below, Changing MTU on your Sabai Router. If your MSS is less than 1400, and you are on OpenVPN, try Changing MSS on your OpenVPN script as well.


Note: If you are on DSL with PPPoE, your maximum MTU is 1492. If you use PPTP, you can not change your MSS.


Changing MTU on your Sabai Router


On your Sabai VPN Router, visit thenetwork page.

In the first drop down next to MTU, change from default to manual. This will allow you to manually change the second field to 1500, the largest allowed by Ethernet. Click Save.

Changing MSS on your OpenVPN Script

If you use StrongVPN as your VPN provider, changing your MSS on your OpenVPN script is simple. If you use another VPN service, please check with that providers technical support to ask how to make this change or look for it under advanced options. Not all providers allow MSS changes.

While logged into your account, look for the MSS & Fragment link under Special Actions. Change the MSS setting to 1300save and export a new script for your VPN Router.

These setting changes will solve most, but not all, MTU lag issues. However, there are many articles available that include more advanced troubleshooting. If you still aren’t happy with your speed, try more speed troubleshooting articles or make an appointment with technical support.


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