Cable modem/server/IP address trick

TheFishingGeek · 06-24-2003, 02:52 PM

I just moved into a new place, and hoped beyond hope that I could get DSL. No dice. So, I'm stuck with cable. Anyway, I have a personal chatroom and webcam on my server, and also use it as a Squid gateway from work. All of this functioning is dependent on me having my home IP address.

When I got the server online last week I was thrilled to see that I had a relatively easy-to-memorize IP addie, and I ran with it. Well, midday today for no apparent reason (server certainly wasn't cycled) the IP changed completely to a horrible number. Comcast didn't used to do this to me, and hopefully this is just a freak thing.

In the event that it isn't, I am curious about what sort of options there are out there to get a server (running Mandrake 9.1) to report changes in IP address, either via email or via FTP upload to another address. I don't recall seeing anything out there, and I'm not qualified enough to be able to script up my own little program to do it.

Thanks for any and all feedback you can provide. I suppose I could keep having my wife email me to get the new IP, but I'd like to find something more automated.

KevinJ · 06-24-2003, 03:36 PM

I would first suggest monitoring the system to see how often the addy changes. That will help in trying to circumvent this process.

Also, I have a script that I use to collect my IP info and send it up to a web page to the server that hosts my subdomain name:

#!/bin/sh

#Getting my IP addy
#
export IPADDR=`/sbin/ifconfig eth0 | grep inet | awk -F":" '{print $2}' | awk '
{print $1}' `

#making my html page
#
echo "
<html>
<head><title>Home for MyDomain.com</title></head>
<body>
<P><center><H1>Welcome to the homepage of MyDomain</H1>
<P><img src=\"MyPicture.jpg\">

<P><a href=\"http://"$IPADDR\""><H1>Click here to enter...</H1></center></
a>

</BODY>
</HTML>
" > /etc/default.html

#sending it into my static server
#
ncftpput -u MyUsername -p MyPassword MyDomain.com / /etc/default.html

Keep in mind that I know next to NOTHING about scripting and HTML coding.. but this is simple enough and it works for me. Anyone with improvments upon the process... feel free to post.

-KevinJ

TheFishingGeek · 06-24-2003, 03:40 PM

That looks like a cool start that I'll have to play with tonight after dinner. Thanks for the help, Kevin!

jharris · 06-24-2003, 04:50 PM

You might also want to look at http://www.dyndns.org - I used to use one of their domains to follow around my dynamic cable modems address. I ran a script that would detect any change in IP address and update DynDNS as necessary.

cheers

Jamie...

miguetoo · 06-25-2003, 09:24 PM

hello jamie.. i'm just getting started with dyndns on linux.. and was wondering how you got the script set up in your system..

edit: nvm.. i just had to add my domain and multiple sub-domains in the ddclient.conf file..

linux rowx..

jharris · 06-26-2003, 05:41 AM

I don't use the update script anymore as I've got a static IP now, but I was just running a script from cron even 5 mins or so. I'll have a dig around and see what client I was using.

cheers

Jamie...

system · 06-26-2003, 08:49 AM

On the off chance that you have a Home NAT Router, many of them have builtin support for Dynamic DNS and will report the IP automatically.

I run an FTP/HTTP box behind a NAT router with dynamic IP. I don't have a domain name, so what I did was to register a fortunecities webpage for free, then I wrote a shell script that can automatically check the IP by logging into my router. It then uploads a simple redirect page on the fortunecities website. I run it as a cron job hourly, though my IP doesn't change unless the modem is reset.

Of course, you can get your IP address from the Linux box if it is connected directly to the cable modem and do the same thing.

If you do have a domain addy already, check DynDNS.