How do I allow Multiple PPTP connections to my Cisco VPN concentrator from the same internet connection.

Posted on 2008-10-29
Last Modified: 2013-12-27
I have two users who work from home, they both share the same internet connection, but only one of them can connect to my VPN concentrator at a time using PPTP.  I need to figure out how to allow multiple PPTP connections to my Concentrator from the same IP address.  Is this possible.  
Question by:Crossroads305
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Expert Comment

by:Michael W
ID: 22830925
Configuring NAT Transparent Mode for IPSec on the VPN 3000 Concentrator

Author Comment

ID: 22834846
Thanks, but I all ready have NAT Transparent Mode configured.  I have no problem connecting multiple users with the same IP when they use the cisco VPN client, its when they use PPTP, which is the way they want to connect, that doesn't allow more than one conncection from the same IP address.
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Accepted Solution

Michael W earned 500 total points
ID: 22837557
Multiple PPTP connections from one single IP to another single IP won't work because the underlying GRE protocol doesn't use port numbers - so theres no way to create multiple GRE streams and differentiate between them.

The issue is that the NAT Engine has to associate the GRE stream with each individual connection, but this is quite difficult as GRE doesn't have simple tags to identify the connection like TCP. The NAT engine doesn't know which client to send the GRE packet to.



Author Closing Comment

ID: 31511138
Thanks.  Now that I know PPTP won't work using the same IP, I moved everyone to cisco vpn client and it works fine.

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