VNC not working over IPsec VPN

  • Hey folks
    I've finally gotten a site to site VPN working using IPsec.
    The remote network has a natted WAN address, but its 1:1 with nothing blocked.
    The connection seems to work as I can use things like SSH and http traffic works fine. However, when I try and use VNC it connects but I just get a black screen. Anyone know why some applications would work and others not? Its it an MTU thing- is there even a way to set that?

    Thanks in advance!

  • Lower the MTU on the wan screen on both hosts to see if it makes a difference.  If this is PPPOE you may want to consider a 1400 MTU (ish).  I say ish because you may need to experiment a bit to find the optimal value for each end.

  • Thanks for the tip!
    I've tried serveral values in the 1400ish range and am not having much luck.
    I am able to make voip calls b/t the two sites, which tells me that traffic is at least flowing in both directions.

    looks like I spoke too soon…. lowering to 1300 seems to have fixed the VNC issue.
    Thanks for the tip!

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