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Dynamic DNS at JTAN

Dial-up accounts, and some DSL or cable modem subscribers, often get a different IP address every time they connect. Although this can enhance your privacy, it means that your location on the Internet is always changing. For ordinary users, this is fine, but if you want others to be able to access your computer, the IP address "moving target" makes it hard for them to connect. What you need is a "dynamic pointer" -- a fixed name that follows your IP as it changes.

JTAN Dynamic DNS service is an easy way for others to locate you on the Internet even if you don't have a fixed IP address. If you want to serve web pages, share MP3s, host Mechwarrior, or run any kind of Internet server, you need a fixed domain name so your users can find you when your numeric IP address changes. Instead of being just a number on the Internet, your server is now always available by the same easy-to-remember name.

How it Works

JTAN Dynamic DNS is available free of charge to any JTAN customer. Your fixed name is automatically assigned the current value of your changing IP. The assignment is established when you log into JTAN using any of a number of services, like checking your mail with POP, or by connecting using dialup PPP. No special software is required.

Dynamic DNS is not enabled unless you turn it on. Typical users, concerned about privacy, don't want people to be able to easily find them on the internet and will not enable Dynamic DNS. However, if you do want Dynamic DNS in order to make your computer easier to find, you can turn it on through your JTAN members page.

You will find your Dynamic DNS configuration page under the "Misc" category in "Account Services" on the lower right of the Members page.

That page will allow you to control the Dynamic DNS options associated with your account on a service-by-service basis using the following checklist.

If you enable Dynamic DNS for a particular service like "pop" and you access that service with POP Mailbox ID "id", then there will be a domain name created automatically pop.id.dyndns.jtan.com defined to point at the IP you used to access the service. In addition, the name id.dyndns.jtan.com will give the IP of the most recent access by any enabled service that was accessed by user ID "id".

Our recommendation for typical dynamic DNS users is to use POP as the service as described above. Pick a specific POP mailbox and have your computer check mail in that box every 5 minutes automatically (MS Outlook will do this naturally when it's running). Most people don't need to do anything extra to set this up -- they already do this. Once you are checking this mailbox regularly, turn on Dynamic DNS for POP, and you will be able to use the domain name "mailboxid.dyndns.jtan.com" to access your computer.

If you have a registered domain, you can create a CNAME that points from some name in your domain, like mypc.yourdomain.com to the dynamic name mailboxid.dyndns.jtan.com. That way you can hide the dynamic aspect of the name. People can connect to mypc.yourdomain.com and automatically find their way to your machine.

It's important to understand that although our Dynamic DNS system is pretty fast, it's not instantaneous. There will be a slight delay from the time when you access JTAN using a new IP address, and the time when your Dynamic DNS is updated. Typically this is less than 60 seconds. We will advertise a 60 second TTL (Time To Live) on your DNS record. Properly designed DNS caches should respect this, but we have seen cases where computers don't immediately "forget" the old address. Malfunctioning DNS caches are out of our control.

Our servers will answer queries for A and TXT records only. The TXT record includes both the IP and the time of last access. The SOA nameserver is "dydns.jtan.com" and this only answers queries about the dynamic zone. It cannot be used as a general purpose nameserver.

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