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How to find out correct MTU value for your ISP

  1. #1
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    Default How to find out correct MTU value for your ISP

    It has been a while since I wrote something useful on this forum so might aswell do it today. I am going to show you how to choose the correct or most suitable MTU value for your ISP to make your browsing experience as best as possible using your current connection.

    Default MTU values for any ISP is normally too high and that results in packet fragmentation which causes unnecessary delays that can be avoided by just choosing a value which is just right for your ISP. Lets now see how we can do that :

    1.Open the “Command prompt” by typing cmd in start menu’s search box and press the enter button on your keyboard.

    2.Copy this command ping -l 1500 -f google.com

    3.Right click in the command prompt and select paste

    4.Hit enter. It will return these values

    C:\Users\Chahal>ping -l 1500 -f google.com

    Pinging google.com [74.125.135.100] with 1500 bytes of data:
    Packet needs to be fragmented but DF set.
    Packet needs to be fragmented but DF set.
    Packet needs to be fragmented but DF set.
    Packet needs to be fragmented but DF set.

    Ping statistics for 74.125.135.100:
    Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),

    5.Select a lower value such as ping -l 1490-f google.com

    6.Keep lowering the number until fragmentation stopps occuring and you will get a stable ping result which would look like this:


    C:\Users\Chahal>ping -l 1470 -f google.com

    Pinging google.com [74.125.135.100] with 1400 bytes of data:
    Reply from 74.125.135.100: bytes=64 (sent 1470) time=99ms TTL=48
    Reply from 74.125.135.100: bytes=64 (sent 1470) time=90ms TTL=48
    Reply from 74.125.135.100: bytes=64 (sent 1470) time=94ms TTL=48
    Reply from 74.125.135.100: bytes=64 (sent 1470) time=98ms TTL=48

    Ping statistics for 74.125.135.100:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
    Approximate round trip times in milli-seconds:
    Minimum = 90ms, Maximum = 99ms, Average = 95ms

    7.Change the MTU value in your Modem/router to the highest your connection supports +28 on top of it. For example you get a value of 1470 then add 28 to it 1470+28 = 1498 so 1498 should be your ideal MTU value.

    The reason we add 28 is because when ping was sent we specified the packet size and that creates an over head of 28 so we add that to the value we get.

    You should now have a smoothly running internet/broadband connection. I hope this helps a few people and if you find this thread useful then please be kind and hit the Facebook like button on top left of this page and also the Google+ button that you would find on the bottom left of this page.

    Thanks
    Last edited by Admin; 20th July 2014 at 03:38 PM.

  2. #2
    Bronze Member HareKrishna's Avatar
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    Wonderful tutorial. I changed mine to 1450 now. It was 1500 previously and my packets were getting fragmented. I find my browsing to be quicker now. I t may just be in my head I dont know but it feels quicker.

    Thanks

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    Its 129 minimum 2@ 100

  4. #4
    I post when neccessary rishabh25's Avatar
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    where can i find this MTU option for my wireless internet?
    Desire is the cause of suffering in Life.

  5. #5
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    Should have a field for MTU size under PPPoE Advance settings or something like that. Depends what router you are using. Some companies just call the same thing by an entirely different name for no reason. Just look around.

  6. #6
    I post when neccessary rishabh25's Avatar
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    i just cant find it on my tata photon's page ;l though i counfigured it out my mtnl connection
    Desire is the cause of suffering in Life.

  7. #7
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    Open command window and try this :

    netsh interface ipv4 set subinterface "Local Area Connection" mtu=1500 store=persistent



    Change the 1500 to whatever the correct value is for your connection.

    You will need to run it under admin user account. This is under the assumption that you are not using wifi.

  8. #8
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    If you are using wifi then just replace "local area connection" with :
    "Wireless Network Connection"

  9. #9
    I post when neccessary rishabh25's Avatar
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    Thx i figured it out
    Desire is the cause of suffering in Life.

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