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VPN in a NATed network

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by eric

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I looked through all the questions posted here and could not find an answer to my question. If my question has been answered before, please direct me to the answer or post below. Thanks.

I am trying to figure out the best way of configuring the VPN to work in a NATed network. I have a Cisco 2620 router that is static mapping my public IP addresses to my internal Servers and VPN NATed addresses. I would like to know how would I configure the VPN?s public and private ports to work with my WIN2K Server, which will be running the DHCP addresses for the Remote Users.

Thaanks for all comments on this matter. If more information is needed, please let me know.

7 replies

by stillatit

I have not tried this, but it MAY work:

Your router should have a feature that maps certain ports to specific internal addresses. Try mapping the ports used by the PPTP protocol to your server and see what happens. (This is also, by the way, whatyou do with your mail server, using the SMTP port.)

Good luck.

by tomjockers

I was about to enable the same network configuration with a Cisco 2620 and Novell Border manager 3.5 when i discovered that for the most part VPN"s don't run over NAT's.
NAT does not know how to "handle" protocol 57 (IPSEC 57)
NAT is able to route/"handle" UDP, TCP, ICMP data only. Any other protocol within the IP payload will be dropped by the NAT box.
The Cisco 2620 can perform VPN with add on software.
A new RFC on NAT/IPSEC support has just been released sorry i don't have the number.You will have to check with Microsoft to verify that their VPN supports NAT.
I will have to upgrade to Border manager 3.6, which supports VPN over NAT to connect some branch offices via there DSL routers

by estebandelatorre

No remote dhcp server needed for remote users, they will use the ip address asigned from another dhcp (from the isp provider)
But if you plan to join two private networks with a vp tunnel, yes you will need a dhcp server at each lan, but with different Ip scopes!!

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