How To Host Web Server On Dynamic IP Address??

Would you like to host a web server or e-mail server on your Internet connection, but don’t want to pay for a static IP address? Dynamic DNS (DDNS) is here to allow you to host that website while still using a dynamic IP address. Previously, this was only available as an executable computer program, or was offered on some small home routers. However, with IOS version 12.4 (and some versions of 12.3), DDNS is now available in the Cisco IOS.

What can DDNS do for me?

The problem with hosting a web server, or email server, on an Internet link that has a dynamic IP address is that your IP address could change. For example, you might register your website as www.mywebsite.com and point it to IP address 20.20.20.20. Later, your IP address could change to 30.30.30.30 and all the users trying to get to your website suddenly cannot connect. You would then have to update your DNS record and that change could take a couple of days to propagate to all Internet DNS servers. The result is some serious downtime for your server.

DDNS solves this issue by monitoring your IP address and, if it changes, that change is immediately reported to your DNS provider. This DNS provider is the only host of that domain and, thus, the DNS record is instantly updated when your IP address changes. There should be only seconds of downtime for any users trying to connect to your web or mail server.

In the Cisco IOS, you must first have the proper IOS to use DDNS. To be safe, any version of IOS 12.4 will work. However, the easiest way to see if you have DDNS available on your router is to go to global configuration and type ip ddns ?. Here is output from two routers. The first router has DDNS, the second does not:

Router with DDNS : " % Unrecognized command"

Router without DDNS : "Update configure dynamic DNS update"

In other words, if you have DDNS, you will receive the option to update your DDNS.

Having DDNS built into the IOS makes it much more reliable than having a PC client. Even better, the IOS offers powerful debugging tools for DDNS by using the show ip ddns update and debug ip ddns update commands. For those who have dynamic IP addresses and want to host a server, DDNS is virtually a requirement. In summary, DDNS is a powerful feature to have available in your Cisco IOS router.