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Unit 6: Domain Name System

access your system instead of an IP address. Being able to access your system using a consistent notes
name in the URL even though the IP address changes is a major benefit of dynamic DNS.
Dynamic DNS (DDNS) is the capability for a host (your Debian server) to update its own DNS
A record. A host’s IP address (or what appears to be its IP address) can change when you use
a home broadband service such as cable or DSL, or when you dial into an ISP (PPP connection)
using a modem. If you have a broadband connection, DDNS allows you to have a full-time
Internet server even though you don’t have a static IP address.
You run a small DDNS client on your server that launch DNS record update requests to the
DDNS server. If you have your own domain name, the DDNS server is the one that’s listed as
the primary name server in your domain record. Most DNS servers do not support dynamic
updates by default. They have to be configured to listen for dynamic updates. When your server
is booted up (or you run the client software manually) it sends a request to the DDNS server
to check/update the IP address in the A record for your server. If you’ve pulled a different IP
address from your ISP since the last time a request was sent, the A record is updated with this
new IP address.
When you use a firewall router, what appears to be your server’s IP address is in fact the IP
address on the “external” router interface. As mentioned on the Networking page, the router
does NAT and this address translation can cause difficulties for dynamic DNS. ddclient is a
DDNS client that works with firewalls, is compatible with a number of DDNS services, and is
available as a Debian package.

Dynamic Dns with your own Domain

You can use dynamic DNS if you previously have, or want to have, your own registered domain
name. You may want your own domain name for several reasons:
1. You would like to set up production Internet servers for an organization or business with
static IP addresses.
2. You would like to use your own domain name with your home server(s).

3. You would like to (as in my case) set up a “non-production” domain just for playing
around with. A non-production domain would allow you to examine how DNS works by
playing around with the zone record values. Being that there are no production servers in
the domain, there’s no problem if you screw something up. (A non-production domain is a
real domain with whatever name you choose but you just use it with test servers. Naturally,
you can make it a production domain at any time just by setting up “real” servers.)
For this I use the Domain Name+DNS Only Service bundle from EasyDNS.com since it kills two
birds with one stone (and because they have toll-free telephone tech support). EasyDNS will
not only host your zone files on their DNS server, but register your domain name (and annually
renew the domain name registration) all for $35/year. That’s a pretty good deal as well as being
convenient. You don’t have to go to one place to register/renew your domain name, and then
go to another place to host your DNS records. When you register a domain name with EasyDNS
they’ll set up some preliminary zone records for you and you just go in and add/modify/delete
records.

EasyDNS offer a Web interface for DNS management so you can play around with the settings,
change server names, create alias records, etc.

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