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Old 11-03-2004, 06:57 PM   #1 (permalink)
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Default Incoming connections blocked

Hi All

I'm looking at a friend's network which has a Speedtouch 510 gateway and acts as a NAT for about 10 workstations. All machines can access the internet and he wants to be able to access them (or at least the gateway PC) from the internet with Radmin (or Pcanywhere), but he can't!

I made sure that Windows 2000 which runs on the gateway PC, didn't have any TCP/IP filtering or its own firewall running. I setup an FTP server on this PC for a trial and told the firewall on the Speedtouch 510 to allow/send packets on ports 20 and 21. That didn't work so I just disabled the firewall completely for a few moments and tried other ports on the ftp server; this didn't help either!

What could possibly be blocking incoming connections?

PS: I'm looking at using nmap to get to the heart of problem, but I don't really know how I should use it. Any ideas related to this would be appreciated.
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Old 11-04-2004, 10:06 AM   #2 (permalink)
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This is a common misconception about NAT.

Routers you buy in the store (most likely) do not have firewalls. They run something called NAT, which accomplishes the same thing as a firewall; however the two are very different.

If you are running NAT, you need to do something called port forwarding, which is sort of like opening a port on a firewall. Here's how it works.

When someone sends an FTP request to your router and the router is running NAT, essentially it doesn't know what to do with the information so it just drops it. Port forwarding tells the router that if some request comes in on port 21 (FTP), then forward it to this computer on your internal network.

Go into the router's configuration and look for something called port forwarding. Basically the information you will need is:

Port range - 21 to 21 (for FTP)
TCP (not UDP)
YourIP

YourIP will be the IP address of the computer running the FTP server (or PCAnywhere client).

To get PCAnywhere to work, you'll have to find out what port PCAnywhere uses and then forward that port to YourIP.
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Old 11-04-2004, 07:45 PM   #3 (permalink)
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Thanks for your reply. I have it all sorted out along the line you describe.
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