Because ISPs don't assign static IP addresses, accessing devices your network remotely is tricky. One way around changing IP addresses is to use a Dynamic DNS service, which automatically tracks the changes to your network's public IP address.

You pobably use your broadband connections for all kinds of things when you're at home, but you can also take advantage of that connection to access devices on your network even while you're away. For example, you might want to view a Webcam, grab files off an FTP server, use a remote access utility like Windows' Remote Desktop, or even access the router itself to administer it from afar.

These sorts of things would normally be made possible by a router's port forwarding feature combined with knowing the public, or global, IP address assigned to your network by your ISP. The problem is that for most accounts, that public address isn't permanent and will change from time to time. It may not change very often — maybe every few days or perhaps even less frequently than that — but once it does, the address you've become accustomed to using won't work anymore. While you can always find the new IP address and begin using it instead, you can't look it up while away from home. Even if you could, the address will eventually change again. 

Static or Dynamic

One way to eliminate this problem is to arrange for a static IP address through your ISP, but this isn't always feasible. For starters, getting one can cost $5 (or much more) a month. With some ISPs, a static IP option isn't available unless you upgrade to a more expensive business-class account (and that pricier service may not even offer any more bandwidth than you already have).

A better solution is to use a Dynamic DNS service that can automatically track the changes to your network's public IP address. These services let you set up your own specific DNS name and then will regularly update a database to make sure the name always points to your current IP address.

Configuring Dynamic DNS

The most common way to use Dynamic DNS is to configure your broadband router to automatically update the service each time it gets a new IP from your ISP. There are several Dynamic DNS services to choose from, most of which are free or available at a nominal cost. The two most popular are DynDNS and TZO. While both services are excellent, we'll focus on DynDNS here because it offers a free version and arguably has the most widespread router support. Almost every router offers some kind of Dynamic DNS support, but your router must support the particular service you want to use. You can access the Dynamic DNS heading in your router's admin interface to see which services it will work with (and you may be presented with additional options if you upgrade to the latest firmware).

Prior to making any router modifications, start here by creating a DynDNS. You'll need to confirm your account via e-mail before you can configure it — once you've done that, look for an Add Host link or go here.

In the hostname field, you can enter anything that means something to you, assuming it's hasn't already been used (let's say joesnetwork, for example). Then pick the domain name you want to use from the rather extensive pull-down list (there are 68 choices in all), make sure your IP address is filled in (it should have been done automatically), and click Add Host.

Now call up the Dynamic DNS configuration page of your router (the exact interface will vary depending on the make and model of your hardware). First ensure Dynamic DNS is enabled, specify the service provider you're using, and then enter your DynDNS user name, password, and the full host name plus domain name you choose (e.g. joesnetwork.dyndns.org). Be sure to apply the changes; a router reboot will probably be necessary.

Remember Port Forwarding and Internal Static Ips

Just as you would if accessing your network via an IP address, before you start using Dynamic DNS you should make sure your router's port-forwarding feature is configured appropriately so the router knows which IP address to forward incoming traffic to. For example, if you're setting up a Web server, forward port 80; an FTP server, port 21; or Remote Desktop, port 3389.

It's also critical that you assign a static internal IP address to any device you're trying to reach so that the router always forwards to the right place. Another way to accomplish this is to use the DHCP reservation feature found on many routers, which will make sure a given device always gets the same DHCP-assigned address.

Using Your New Domain Name

It may take up to an hour after you set up your DynDNS domain name before it's usable. Once active, all you need to do is use the domain name instead of the IP address with the relevant software. The nice thing about Dynamic DNS combined with port forwarding is that you can use the same name to access multiple systems on your network. As long as you've set up the port forwarding correctly, the type of software you use or port you specify will determine what you connect to.

Although the domain names that DynDNS offers aren't particularly memorable, they're probably sufficient as long as you're the only one that needs to know them. If you plan to allow others access to your network and want to use a more meaningful name, TZO offers a Dynamic DNS service that will let you choose a custom domain name for about $60 a year.

A final caveat: Be sure to check your ISP's terms of service before setting up a server that's going to be public and generate lots of traffic (especially a Web server), because some ISP rules prohibit customers from running such servers (particularly with consumer-grade accounts). It usually won't be an issue when you're setting up personal access, but in some cases ISPs may filter incoming traffic or terminate your account if it detects an unauthorized server. (Another of TZO's paid services provides a forwarding feature that will let you run a web server even if your ISP blocks port 80.)

There you have it. We've only scratched the surface of what Dynamic DNS can do, but the most important thing to remember is that it will ensure that your network is always locatable no matter how often your public IP address changes.