Windows 8 and 8.1 Forums


Certain TCP protocols are blocked in outbound traffic?

  1. #1


    Posts : 2
    Windows 8

    Certain TCP protocols are blocked in outbound traffic?


    Ok, so my computer was having connection problems, and basicly, when I did the scan, this came up.
    "Your system can not send or receive fragmented traffic over IPv6.
    The path between your network and our system supports an MTU of at least 1280 bytes. The path between our system and your network has an MTU of 1276 bytes. The bottleneck is at IP address 2001:470:0:136::2. The path between our system and your network does not appear to handle fragmented IPv6 traffic properly."

    I have no idea what this is and how to fix it.
    Ideas?

      My System SpecsSystem Spec

  2. #2


    Posts : 2
    Windows 8


    Scan- ICSI Netalyzr
      My System SpecsSystem Spec

  3. #3


    Sloe Deth, Californicatia
    Posts : 3,908
    Windows 8 Pro with Media Center/Windows 7


    Number one, does your ISP use IPV6? Because I have Cox and I don't have that protocol.

    Unless you actually use IPv6 I would not worry about it, I'd disable the protocol in my Adapter settings, it causes a lot of problems it you have it turned on and your ISP does not actually use it.
      My System SpecsSystem Spec

  4. #4


    I beg to differ on the IPv6 comment.

    The Argument against Disabling IPv6
    It is unfortunate that some organizations disable IPv6 on their computers running Windows Vista or Windows Server 2008, where it is installed and enabled by default. Many disable IPv6-based on the assumption that they are not running any applications or services that use it. Others might disable it because of a misperception that having both IPv4 and IPv6 enabled effectively doubles their DNS and Web traffic. This is not true.
    From Microsoft's perspective, IPv6 is a mandatory part of the Windows operating system and it is enabled and included in standard Windows service and application testing during the operating system development process. Because Windows was designed specifically with IPv6 present, Microsoft does not perform any testing to determine the effects of disabling IPv6. If IPv6 is disabled on Windows Vista, Windows Server 2008, or later versions, some components will not function. Moreover, applications that you might not think are using IPv6—such as Remote Assistance, HomeGroup, DirectAccess, and Windows Mail—could be.
    Therefore, Microsoft recommends that you leave IPv6 enabled, even if you do not have an IPv6-enabled network, either native or tunneled. By leaving IPv6 enabled, you do not disable IPv6-only applications and services (for example, HomeGroup in Windows 7 and DirectAccess in Windows 7 and Windows Server 2008 R2 are IPv6-only) and your hosts can take advantage of IPv6-enhanced connectivity.

    Support for IPv6 in Windows Server 2008 R2 and Windows 7
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  5. #5


    Posts : 467
    Windows 8 Pro


    back to his problem , it looks like your PC (IP 2001:470:0:136::2) is set up to use a MTU of 1276 for some reason , can you look at the configuration of it's IPv6 settings and see if thats where the problems is?

    it's unusual if it is as the MTU is normally between 1460 and 1500.

    Last edited by Wullail; 13 Oct 2013 at 07:06.
      My System SpecsSystem Spec

  6. #6


    Joisey
    Posts : 315
    Windows 8.1 consumer 64 bit


    Quote Originally Posted by Wullail View Post
    back to his problem , it looks like your router (IP 2001:470:0:136::2) is set up to use a MTU of 1276 for some reason , can you look at the configuration of it's IPv6 settings and see if thats where the problems is?

    it's unusual if it is as the MTU is normally between 1460 and 1500.

    I think the MTU is set in the computer networking settings, not the router. As always, I could be wrong. :-)

    On another note, I did not realize the IPv6 was even in use yet. Is there a site I can go to to or some other way to see if my setup works with IPv6?
      My System SpecsSystem Spec

  7. #7


    Posts : 467
    Windows 8 Pro


    Try the following....substituting ipv6 instead of ipv4 if thats where the problem lies.


    Change your MTU under Vista, Windows 7 or Windows 8 richard-slater.co.uk
      My System SpecsSystem Spec

  8. #8


    Quote Originally Posted by JuviaFoxface View Post
    Ok, so my computer was having connection problems, and basicly, when I did the scan, this came up.
    "Your system can not send or receive fragmented traffic over IPv6.
    The path between your network and our system supports an MTU of at least 1280 bytes. The path between our system and your network has an MTU of 1276 bytes. The bottleneck is at IP address 2001:470:0:136::2. The path between our system and your network does not appear to handle fragmented IPv6 traffic properly."

    I have no idea what this is and how to fix it.
    Ideas?
    Absolute rubbish and this very likely has nothing to do with your connection problem. This test is only explaining that your ISP doesn't handle IPv6, and most don't so this is no surprise. I've run that test with the same results and there is nothing wrong with my connections.

    And turning off IPv6 is definitely not an option here as Windows uses the IPv6 protocol internally for many things as was explained in the link I posted earlier.

    If you are having a connection problem please post the ipconfig/all form this machine and I will be happy to help.
      My System SpecsSystem Spec

Certain TCP protocols are blocked in outbound traffic?
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