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Author Topic: Why would lowering my router's MTU to 1224 on VDSL stabalise download speeds?  (Read 488 times)


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I've had a speed drop issue when downloading files for several years now. Every 1-2 minutes the download speed would sharply drop to around 30-27mbps, then return to normal. The speed of my VDSL line is 51mbps (router downstream is synced at 54081 kbps currently). I'm connected to an ECI cabinet and my router is an Archer VR200 (with a Lantiq modem). My ISP is Talktalk.

I believe I've finally fixed the issue simply by lowering my MTU on the router's web interface to 1224 (default is 1500). Now, the download speed stays fairly constant 51-48mbps). I've tested this 4 times now by downloading a 1Gb file (from without the speed sharply dropping. I also noticed that the connection reaches it's top speed noticeably quicker.

I tried other MTU values a few weeks ago, but this seemed to reduce the max and average download speed.

Update - Did a bit more testing with an MTU of 1224 and still got drops in my download speed every couple of minutes. Could the drops in download speed be caused by my ISP TalkTalk?

Actually, I think it might just be homeplugs interfering with the VDSL frequencies.
« Last Edit: December 10, 2019, 03:32:27 PM by cbdeakin »


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Always use ethernet for this type of testing.
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