Fine Tune your MTU settings to improve Broadband speed

Published 13/04/2005 14:15   |    Updated 25/03/2009 17:50
How do I tweak the MTU settings on my Windows XP computer?

One of the more technical obstacles to broadband clipping along at its expected rate is a setting called the maximum transmission unit (MTU).

When your PC requests data from certain websites, they use Path MTU Discovery to check what size packets to send back to your computer. If the site can’t check what size packets to send, it reverts to the default of 1500, but if any of the gateways or routers along the path have a smaller MTU the data packet will be dropped.

You can tweak the MTU settings on both your PC and your router, but you must ensure you use the same figure on both. ADSL Reports provides a clear guide on how to adjust MTU at

The free Speed Guide TCP Optimizer (link to external site*) will determine the optimal MTU and other settings for your XP machine. Make sure you back up the Windows Registry of your PC before changing anything.


*Please note! BT cannot be held responsible for the content or advice given by external websites, nor the result of misconfiguration arising from such advice.



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