From: mike-newsgroup@-DELETETHISPART-.upcraft.com   
      
   Konstantinos Agouros wrote:   
   > In <0gX_e.9959$1M7.8762@fe12.news.easynews.com> Mike Drechsler - SPAM   
   PROTECTED EMAIL  writes:   
   >   
   >   
   >>Kai Schaetzl wrote:   
   >>   
   >>>I'm trying to establish a VPN tunnel from my laptop over GPRS to my office   
   >>>LAN. VPN works fine from broadband or dialup, but GPRS fails.   
   >>>   
   >>>Client is Windows XP, Server is pptpd/pppd on a Snapgear appliance, mobile   
   >>>provider is O2 Germany.   
   >>>It seems the GPRS connection works via NAT and that this may be the cause   
   >>>of the problem. The log shows "LCP: timeout sending Config-Requests" which   
   >>>might also indicate that my side couldn't answer because of NAT.   
   >>>   
   >>>Is there anything I can do about that concerning the server configuration?   
   >>>I do have good knowledge about Linux and partly about networking but   
   >>>exactly none about pptpd/pppd, I just use the web interface provided by   
   >>>the router. I can edit configuration files (pptpd.conf and options.pptp as   
   >>>I understand) directly if necessary.   
   >>>   
   >>>Other possible causes might be MTU or the GPRS gateway not allowing highly   
   >>>encrypted authentication. I tried everything down to even no   
   >>>authentication, nothing worked over GPRS. MTU seems to be at normal 1500.   
   >>>So, I think both are not relevant here.   
   >>>   
   >>>Kai   
   >>>   
   >   
   >   
   > Are You sure, that Your VPN-Software can cope with NAT-traversal?   
   > Microsoft PPTP stuff uses GRE and this can not be natted.   
   >   
   > Konstantin   
      
   Yes it can be "natted" if the device has an application layer gateway   
   for the pptp protocol.  A great many consumer level routers using NAT   
   have supported an ALG for PPTP for many years.  The hard part is   
   supporting multiple simultaneous sessions through the NAT gateway but   
   there have been implementations that seem to work with multiple PPTP   
   sessions active at the same time so it's not impossible.   
      
      
      
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   Mike Drechsler (mike-newsgroup@-deletethispart-.upcraft.com)   
      
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