router timeout/keepalive problem?

[BrettT]

using digiTunnel 1.4.4 on OSX 10.4.11 on a G5 iMac

One of my VPN connect-to sites is transitioning to a new PPTP server (Fortigate branded router).  The old system is referred by them as "the proxy server" which I assume is an old clunker PC running some software. 

I connect and function fine with the "proxy server" and have for years using digiTunnel.
The problem is with the new Fortigate connection:  I authorize and connect fine and function fully for "a while" - a couple of minutes.  But then the connection freezes/stalls.  If I disconnect digiTunnel and reconnect then things pick up where they left off.  I use a DIRECTORY command of an entire disk to demonstrate the behavior. 

This has been bothering me for a long time and I've spoken to Paul about it before.  It doesn't have anything to do with digiTunnel, it has something to do with the routers I'm traversing here at home.  I first discovered that everything works fine if I take the laptop out to a public WiFi site.  So I tested bypassing my routers here at home (1 in the apt, another for the building) and everything works fine then also.  FYI, a WINDOWS XP system on my desk has absolutely no problem making and maintaining this VPN connection.

Today I made another discovery:  if I issue TRACEROUTE commands regularly to a site in the tunnel, then the VPN connection works fine and does not freeze or stall.  I setup a terminal window with a ( sleep 10; traceroute ... ) loop and the VPN connection stays active.  A 30 second sleep was not effective and I have not tried any other values yet.  Doing the same thing with PING does not help.

So any thoughts would be greatly appreciated on what may be going on here and where to look on the router for some setting to investigate.

thanks

[Paul Collins]

Hi Brett,

That's interesting about traceroute. Since you seem to do fine at the public wifi site, that does suggest that your router doesn't handle the new server's traffic well for some reason. You might check if a firmware update is available for your router. I'm not aware of anything DigiTunnel could do differently to "keep awake" a connection. To investigate further, it might be interesting to do packet sniffing on your PC to see what it's up to that keeps the connection up.

I'm not aware of any settings for routers in general that would do this--the most I usually see is "pptp-passthrough ON/OFF". Your router may be different and it might be worth a look through its manual.