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How do I configure NT to be a gateway to an ISP?
John Savill
October 20, 1999
2 Min Read
A. Firstly the hardware required would be a network and amodem. The network card would be so the other clients in the network cancommunicate with the "to be" gateway, and the modem to connect to thegateway. Dial-up networking is not covered here, and you should first beconfident with dial-up networking before attempting this.
Start the registry editor (regedit.exe) and add a value of type DWORDcalled DisableOtherSrcPackets in theHKey_Local_MachineSystemCurrentControlSetServicesRasArpParameters area,and set to a value of 0. This is so packets that are sent through the NTgateway, the original IP address stored in each packet is retained, i.e. ofmachine a is sending a packet through b, then the packet retains the IP addressof a, rather then be automatically changed to b. Also changeHKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesTcpipParametersIPEnableRouterto a value of 1.
On the gateway machine ensure TCP/IP is installed with a static IP address,and a correct subnet address (usually 255.0.0.0 for a class a, 255.255.0.0 forclass b, and 255.255.255.0 for class c). Make sure the default gateway addressis blank.
Install Dial Up networking and configure for NT to dial out only. You willhave to reboot
Add a phonebook entry for your ISP as you would as normal, however uncheckthe "Use default gateway".
Enable the PC to be able to forward IP packets, by starting control panel,double click Network and choose the protocols tab. Select TCP/IP and thenrouting. Check the Enable IP Forwarding. You will need to reboot
If when you connect to your ISP you are given an IP address, you will needto connect to your ISP, and then find out which IP address you are given. Toget the address type
IPCONFIG
Look for a Wan adapter and write down the IP address. If you know your IPaddress before you connect you can forget this step.Add a route for the IP address used when connecting to the ISP (the oneidentified in step 6)
route add 0.0.0.0 mask 0.0.0.0 metric 2Configure all clients gateway as the network card IP address of the NTgateway.
This would enable the machines to send out IP packets to the internet,however the packets would have no way of finding there way back, as the ISPwould not know to route them through the gateway, so you ISP will have toeither a) have host entries for each of the machines or b) point to the gatewayas another DNS.
Other things to check are as follows:
Make sure your ISP routes packets to you otherwise you will be able to sendpackets out but the replies will never be get to you
Make sure your local IP networks (each machine can ping each other) andthat all PC's have a valid internet address. If you do not have internetaddresses for each PC that have been assigned from InterNic then you will needsomething like Proxy Server instead.
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