a developer's notes – a semi-technical web development BLOG

June 20, 2012

Can’t connect to FTP server with External IP address on Verizon Fios with an Actiontec MI424WR router

Filed under: Daily Computing — Duy Nguyen @ 8:56 pm
Tags: , , , , , , , , , ,

ISSUE:

Unable to connect to a FTP site that is hosted on a PC, using the external IP Address. I am prompted with a authentication dialog box, but after you enter in the credentials, the web browser indicates that it is unable to connect.

BackGround:
1. Port forwarding on the Verizon Router has been configured to forward port 21 (TCP) to desktop
2. Internal IP address works ftp://192.168.1.5/
3. Using the external ip ftp://xx.xxx.xx.xx, prompts for credentials. After using the same credentials to log in, I get the following error:

IE: Internet Explorer cannot display the webpage

After speaking with an Actiontec rep, they told me the issue is that the MI424WR router does not support “loopback”. In other words, the router expects connections to the public
IP only from the external interface. It will ignore and drop traffic to the public IP from the internal interfaces, thus when you are attempting to access your machine with a public IP from within your LAN, the public IP is causing the local machine to contact the default gateway (your router) and your router is not forwarding that traffic back to your host machine.

When the tech attempted to connect to my FTP site with my external IP, he entered the ftp account and password and got right in. Basically, you can’t test this from within your home network, because of the non-loopback support. You will have to ask a friend or neighbor to test it for you. Or connect to another network OUTSIDE YOUR NETWORK to test.

I didn’t have this issue with Comcast, because Comcast only supplies you with a modem. I was using my own router. With Verizon Fios, they supply you with a router/modem in one device. So their router is made differently.

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