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Port Forwarding with a modem and router

Last response: in Networking
October 16, 2010 4:10:45 PM

Hi guys:
I've been having some problems trying to forward some ports, I will try to explain what I have configured:
I have an ADSL modem and a wireless router connected to it through ethernet cable, my router is configured as Automatic DHCP, and the ip address of my router lets say it is
Now the local IP address on my router lets say it is, so the IP address on my PC is for example, and it is static.

If I want to forward ports in my network, what I do is add those ports on my router, and tell it that I want to forward them to my IP address ( and then save settings. BUT, it seems that is not working, so here comes my question...

Do I need to forward ports on my modem also?, OR, how do you open ports when you have a modem and then a router on your network?... because it seems that the way that I'm doing it is not working...


Best solution

October 17, 2010 3:21:30 AM

You only need to port forward on the router. Beware, it’s quite common for dsl ISPs to provide an all-in-one device, a combination dsl modem+router. If you then place your own router behind such a combo device, you’re double NAT’d, which means you will have two firewalls to manage. In that case, you’re usually better off to place the dsl modem+router in “bridge mode” which effectively disables the router features and demotes it to just a modem.

Even if you have port forwarding setup correctly, there are couple things to watch out for. Make sure you open those same ports on any *local* firewalls, such the one provided by Windows or any third party anti-malware you may have installed (e.g., Norton, McAfee). Also, some ISPs *block* certain ports. If that’s happening, it obviously won’t matter what you do w/ your own firewall(s) as the traffic is being filtered out upstream. You might need to temporarily connect to the ISP without a router and local firewall (if any) disabled to confirm if this is the case.

October 18, 2010 3:55:10 PM

The modem that I have is the CTC Union Atu-R130, it has just 1 ethernet cable, and the router that I have is the Linksys WRT54G2 v1.5...
So with this kind of devices what should I do to configure my network?

And I understand that my ISP will have some ports blocked, but as far as I know, right now all of the ports that I'm trying to open are NOT working :/ 

Thanks for your answer
November 3, 2010 6:03:27 PM

Best answer selected by Xtrastor.