Obtaining a Domain Name

If you want to set up your own domain on a private subnetwork that's either not connected to the Internet or that's connected via a NAT router, you can use any domain name you like, albeit with some caveats. The main risk is that your fictitious domain name might match a domain that's already being used by somebody else. Even if it's unused today, it might be registered tomorrow. In this case, you'll be unable to reach that other domain's computers unless you reconfigure your network in some way. If your domain name creeps into outgoing network traffic, such as e-mail you send, the result can be confusion or even failures of the network protocols. For these reasons, if you use a made-up domain name, you should use one that's in a top-level domain (TLD) that's completely fictitious, such as .invalid. For instance, you might call your domain mydomain.invalid.

Another approach to obtaining a domain name is to register one. Dozens, if not hundreds, of domain registrars exist. These companies register a domain you select in your name, so you can use the domain in question for any purpose. Registering a domain is a necessity if you want to use your domain name on the Internet at large. If you register a domain, you can, of course, use names in that domain on your own network, including any segment or segments that aren't visible to the Internet as a whole. The cleanest way to do this is to use separate DNS servers for local use compared to Internet use. For instance, you might contract with a DNS service provider to handle your domain on the Internet, but run your own local DNS server that includes additional local-only entries.

To find a domain registrar, consult a list, such as those maintained at http://www.newregistrars.com and http://www.icann.org/registrars/accredited-list.html. You'll be able to obtain a domain in a popular TLD such as .com, .net, or .org. Some countries have made their TLDs available commercially, so you can obtain a domain in .cc, .tv, or others fairly easily, as well. If you want a domain in a specific country's TLD, consult http://www.iana.org/cctld/cctld-whois.htm for contact information. In the past, domain registration cost $70 for a two-year lease on a domain, but with so many competing registrars today, domain name lease times vary and costs seldom exceed $20 a year. Most registrars offer DNS services, either as part of domain registration or in a low-cost add-on package. Of course, these DNS services don't provide the advantages of running a DNS server on your own network, but they're usually quite adequate to enable users on the Internet at large to locate your servers.

A final option lies in between these first two options, and is appealing for those with broadband Internet connections that provide variable IP addresses: You can use a dynamic DNS service. These services enable you to use a hostname or a subdomain name within the range provided by the dynamic DNS provider. If you run appropriate software, you can keep forward lookups pointing to your IP address, even if it changes frequently. For lists of dynamic DNS providers, consult http://www.technopagan.org/dynamic/, http://www.geocities.com/kiore nz/, or http://dns.highsynth.com. Once you're registered, you can then run a local DNS server as authoritative for your subdomain, but let the dynamic DNS service handle external lookups, which would normally all point to your single external IP address.

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