Forum Discussion

schan's avatar
schan
Newbie Caller
3 years ago

PPTP not working

My PPTP VPN connection to my work is not working with T-Mobile Home Internet service.  I tried to call tech support multiple times but none of them had a clue what I was talking about.  Is other people experiencing the same issue?  Is there anyone able to get their PPTP VPN working on T-Mobile Home Internet?

BTW, my other VPN connections like IPSec and Open VPN works.

  • djb14336's avatar
    djb14336
    Bandwidth Buddy

    Yeah... that is not good.  Can't open/forward inbound ports because of TMO's XLAT464/CGNAT fiasco.

     

    You pretty much HAVE to be doing the whole stateful thing for it to work (connection details retained/session kept open and packets coming back in the same way they went out).

    P2P style traffic can get monkeyed up pretty bad on their networks because of the screwy IPv6 VPN style tunnel crud.

  • djb14336's avatar
    djb14336
    Bandwidth Buddy

    The usual culprit is packet size.  Largest I have seen pass without fragmentation is 1440, others have reported 1420.

     

    So the client likely needs to have it's MSS manually set to something like 1400 or 1380 (lower if it needs more space in the header).

  • schan's avatar
    schan
    Newbie Caller

    Thank you very much for your reply.  I set the MTU to 1000 but my PPTP connection still didn’t go through.  It says “A connection to the remote computer could not be established, so the port used for this connection was closed.”  When I use the same setting with my Cox internet connection, it went through without any problem.

  • bzafar19's avatar
    bzafar19
    Network Novice

    I am having similar issue PPTP connection not working for me