Cannot ping cable modem's public address or connect to it from other locations. Please help.

Posted on 2006-04-16
Last Modified: 2008-03-10

This is my issue:

I have Optimumonline cable modem. I would like to have a FTP server on my Windows XP PRO machine for my personal use, I went to and got myself an account which is all setup and functional. I am using a linksys WRT54GS routher which has port 29001 enable for FTP. By the way, optimumonline would not allow transmission on FTP default port 21. Router is configured to port forward to the PC which is running FTP. My public IP Address was verified by going to

I installed SERV-U FTP server and created the FTP domain which went very smooth. After installation, I connected to the FTP server locally via FTP client which was success. So all seem good and fly but here are issues:

If I go to my other location or friends house and try to ping my Public Ip address, I get nowhere. ERROR("HOST UNREACHABLE"). I cannot ping the IP Address at all.
I have setup my router for remote administration at port:8080. So when I type in my public address assigned by my cable provider (, browser times out.

I am able to ping the router locally. I have not enabled my router to block http pings so I should be able to ping the router or connect over http.

Thanks you.
Question by:ultrajeepster
    LVL 12

    Expert Comment

    does your cablel modem have a built in router?

    are you pinging the IP or the dyndsn site you created? if the dyndns, is the ip translation accurate?

    sounds like you have everything right, otherwise....some firewall somewhere.. you have xp sp2? disable your firewall.


    Author Comment

    Hey Craig,

    Thanks for looking into this issue. XP firewall was never on. Cable is hooked up to a Motorola modem which doesn't have any router or firewall. Since last night weird things are happening such as:

    I can no longer connect to the FTP server locally yet SERVE-U FTP server is now able to run on port 21. I was never able to have the FTP server up and running on port 21.

    I am pinging the address that I got from


    Author Comment

    I have figured out the issue. This might help other SERV-U users as well. What I found out is that Serve-U would start windows but will not allow connection if you are using any port than FTP default port 21. In order for you to use other ports, you need to go into the user interface once the windows bootup and change the port to (perhaps 21 or in my case I was using 15003) and hit F5 key to refresh which will change the FTP server to active and then you can switch back to whatever port you like and hit F5 again. I would love to run it on Port 21, but I think my cable provide doesn't like it. If your provider doesn't have any issues with you running your FTP server on PORT 21 then there are no changes required at all. You just boot your PC and the SERVE-U FTP server would start up on default port 21 and off you go.

    LVL 12

    Accepted Solution

    Cool. good job. thanx for letting me know that info. it will definately come in handy!

    LVL 4

    Expert Comment

    Alternatively, you can run the server on port 21 on your pc and do port forwarding on the router.  Set incoming port to 29001 and destination port to 21 with the IP of your box behind the firewall.  This way, you don't have to make the changes to SERV-U each time.

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