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MTU size on router... change?


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kiddingguy

I just came across an article on MTU. Looks promising!

As an example/“proof” the download speeds went from 150 to 450 Mbps.

 

Is this a safe way to optimize the internet connection speeds? Is this seen as  “cheating” by my ISP? And is it ‘safe” to alter these values into my router? What can go wrong?

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+BudMan

And what article/proof was this that changing your mtu would change your speed from 150 to 450?

 

Seems really unlikely unless your mtu was set way to low to begin with..   For example if you were using a mtu of 576 (very lowest normally) and you went to 1500 (normal standard mtu)

 

Do the math to what your MTU could do..

(MSS/RTT)*(C/sqrt(Loss)) [ C=1 ]

 

So with the standard MTU and a 80ms RTT without any loss your max would be  1460.00 Mbit/sec.

 

With even a very low mtu say 576, and same 80ms RTT your max would be 536.00 Mbit/sec.

 

So while sure MTU could and can affect your speed.  I find it highly unlikely that a change would give you any such speed boost..

 

There are many factors that could effect your overall speed..  The mtu should normally be set at standard 1500 and Path discovery would adjust this down to prevent fragmentation for any given conversation between source IP and dest IP across the internet.

 

Now if your using some other form of connection.. PPPoe for example, or your over a vpn of some sort then the correct mtu would be less than the standard 1500 ethernet size..  But I really do not see adjusting accounting for such a boost in performance.

 

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kiddingguy

It's a YouTube video actually.

Don't know if it's legit or actually doable. There's a lot of bs on YT.

 

Also, other sites have mentioned changing MTU and receive higher speeds. Not by so much, but higher.

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+BudMan

And who's ethernet interface would ever be at 576 to start with?  Yeah if your setup was that messed up, correcting it would be a good thing yes.

 

$ netsh int ipv4 show int

Idx     Met         MTU          State                Name
---  ----------  ----------  ------------  ---------------------------
  1          75  4294967295  connected     Loopback Pseudo-Interface 1
 14           5        1500  connected     Ethernet
 13          25        1500  connected     Ethernet 2
 17          20        1500  connected     Ethernet 3

 

As you can see mine is 1500.. Lets change that to see if drops my speedtest into the dirt.

 

So before test

before.png.fcd2970dedbc1fcbb6c796e0d6f63c66.png

 

Now changed it to 576, which Yeah if your ethernet is set to 576 then its borked anyway ;)

 

C:\Windows\system32>netsh int ipv4 show int

Idx     Met         MTU          State                Name
---  ----------  ----------  ------------  ---------------------------
  1          75  4294967295  connected     Loopback Pseudo-Interface 1
 14           5         576  connected     Ethernet
 13          25        1500  connected     Ethernet 2
 17          20        1500  connected     Ethernet 3

 

Yeah my speed drops... But it sure not as drastic as down to 150ish..

576.png.3f9385d39eb2abb9dba8bcacf6cedd0e.png

 

If I would take anything out of that video - is yeah to make sure your mtu is not borked.. There should never have been a reason for windows to alter the mtu of an ethernet connection or your wifi connection.. Unless you ran some sort of tweaking nonsense software, etc. etc..

 

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erpster3

changing the MTU value does very little or NOTHING to affect broadband/ethernet/LAN/Wifi internet speeds (and in some cases it may make things worse).
setting MTU to 576 was only necessary for optimizing dialup internet connections in the late 1990s & early 2000s when using dialup modems back in those days

 

so I consider that YT video to be "fake news"

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+BudMan

^ yeah... Lets make some video that will grab attention.. And while its not actually wrong in that a wrong set mtu could effect your speed.. The odds of someones mtu being so wrong is just nonsense... Now I could see if you were running some vpn software or something on your machine.. Say for work, it might adjust down your mtu, or set a mss value that is lower to account for the overhead of the vpn tunnel.. The old cisco vpn clients could do this for example..  But it would be something like 1310 or something like that.

 

But I just don't see how anyone's machine would have their ethernet set down to 576.. Without some major intervention from the user doing something they really shouldn't be doing in the first place.

 

For sure I would label it click bait title.. Like saying Add 10 years to your lifespan.. And then telling you to not smoke ;)

 

So its like this video ;)  yeah if your mtu is 576 its F'd up ;)  Adjust it to what it should be will make a difference in your speed.  Just like smoking is bad for you, if you don't smoke you will prob live longer than someone that does hehehe

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