problem with router---NAT and caching?

From: Phillip Helbig---remove CLOTHES to reply (helbig_at_astro.multiCLOTHESvax.de)
Date: 04/02/05

  • Next message: Larry Kilgallen: "Re: Finding The Right Path For Your VMS Applications" 
    Date: Fri, 1 Apr 2005 23:33:14 +0000 (UTC)

    For a long time, I've had a DSL router forward incoming requests to a
    particular internal address (the cluster alias if it is a cluster, the
    address of a particular machine if that is what is behind the router).
    This works OK. I'm testing out some hardware, so I set up another
    machine with another IP address and told the router to forward incoming
    connections to that. Works OK.

    I then go back to the original setup. EVERYTHING works OK, as it did
    before, EXCEPT incoming stuff over port 6000 (remote application
    displaying locally). It's not a security problem; the only thing I
    changed---and changed back---was the address which the router forwards
    stuff to.

    I've tried everything I can think of---changing the address on the
    original machine to that of the new machine (where the displaying
    worked), tried remote applications at a variety of remote nodes. In all
    cases, EVERYTHING works fine---incoming and outgoing connections over
    any port---EXCEPT that remote applications can't display locally.

    I then went back to the new machine. Everything works fine, including
    remote applications which display locally.

    I'm thinking that the router doesn't really forward incoming connections
    to an internal IP address, but rather to a certain MAC address. Thus, I
    could give it a new MAC address with a new IP address and that would
    work, but it got confused when I tried to go back. OK, so I turned off
    the router for half an hour and then tried again, hoping that any such
    cached information (this is speculation) would disappear. The problem
    remains.

    The error message I get at the remote node is the standard

       X Toolkit Error: Can't Open display
       %DWT-F-NOMSG, Message number 03AB8204

    Years ago, I had a similar problem---everything except port 6000 worked
    OK---with another router. After a while it went away, but I never
    understood why. Since then, I haven't noticed the problem again.

    Is there something special about port 6000 with respect to NAT which I
    am not taking into account? If I forward all incoming stuff to a
    particular internal address, and incoming and outgoing connections over
    other ports work, it is a bit strange that only port 6000 doesn't work.

  • Next message: Larry Kilgallen: "Re: Finding The Right Path For Your VMS Applications"

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