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DaveWWWFlag for Canada

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Port forwarding through 2 routers

Port forwarding failing.  Here is the info:

1. I have a remote client (too far away to visit) who needs port 8400 forwarded to a local workstation for remote users.  

2. They have their ISP's DSL (I think it's a 2wire model) set up as a router (DHCP issuing LAN IP addresses on 192.168.2.xxx).  No local clients are using this except...

3. ...They have a cable coming out of the ISP's lan port to the WAN port of a Linksys router.

4. The Linksys router has a WAN IP of 192.168.2.10 and works fine - everyone connected to the Linksys is getting on the Internet.

5. The Linksys DHCP is issuing IP's on 192.168.1.xxx.  (Not sure why they have this particular router-to-router setup)

6. To make port forwarding work, on the ISP's router I forward port 8400 to the Linksys WAN IP (192.168.2.10). On the Linksys, I also forward 8400 to the IP address of the desired workstation 192.168.1.105.

I cannot communicate over port 8400.  I've done this before with another client and it was as smooth as silk. What am I missing?

Thanks for any help.
Dave
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piattnd

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Tom Scott
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I have a similar setting working :  I even forward ALL ports to the second router, which is not a real router, but a NAT gateway, and so are yours...

The tests proposed by TomRScott seems relevant to me.
In order to check ONLY port 8400, you can use a telnet command to the exposed IP address.
From "the Internet":
telnet <ISP's public IP address> 8400
From "192.168.2.x":
telnet 192.168.2.10 8400
From 192.168.1.x:
telnet 192.168.1.105

If you have the same results each time, it might mean that port forwarding is working OK but that you actually need more ports to have the application/service/daemon listening on TCP/UDP 8400 on 192.168.1.105 working as expected.

BTW: be careful, forward UDP/TCP 8400 accordingly to the settings of the app/service/daemon. If you don't know, forward both!
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Hello all, and thanks for the help.  I was not able to test from within 192.168.2.0 except from the 192.168.2.1 router, which was able to reach the router at 192.168.2.10, since I was remoted into that 2nd router which was issuing IP addresses on 192.168.1.0.

Anyway, I agree with TomRScott that it "sounds" correct, and in fact I am doing this exact arrangement with another client with no problems at all, and basically sets up a guest network.  And inside the clinic, other workstations are communicating with the router over 8400, so it is a matter of traffic not making it through.

Because I have no need for the two router arrangement, I set the innermost router to PPPoE, saved the settings and had them reset the first router, which defaults as a DSL modem upon reset.  The problem was solved. :-)