In its original design, all IP addresses had to be assigned by the central registry. However, modern Internet managements use unregistered IP addresses in various context. Those unregistered IP addresses are generally called private IP address.
There are several uses of private addresses. For example, my own in-house LAN uses private addresses. It is a common practice to assign private addresses on a small network that has limited (or totally no) connection to the Internet.
Domain names should be registered. However, registration is not essential for building an isolated network. With appropriate management and careful operation, it is possible to connect an unauthorized domain name based network to the Internet safely.
In this page, we call a network based on unauthorized domain names a bootleg. (Please note that this is not a common term.)
The author operates his in-house LAN with private IP addresses. It is just suitable for a small network as his. Usually, hosts on a private address based small network have no domain names. However, his network is assigned an unauthorized domain name (bootleg.)
There are two major reasons to use bootleg:
On what points it is better?
/etc/hosts and/or LMHOSTS) if there are many PCs on the LAN.Moreover, there is a problem of reverse lookup.
Some applications do reverse lookup (i.e., resolve an IP address to a domain name.) If you take care nothing about domain names, reverse lookup against private address on the LAN will be recursed to an external DNS server for a domain 168.192.in-addr.arpa. (if the LAN uses a subnet in 192.168.) An application did reverse lookup will be blocked until an answer is received. If the Internet connection is via dial-up, a connection will be established everytime an application tries to do reverse lookup.
You might say, "OK, run a local DNS server to resolve reverse lookups in the LAN." But, it is not so simple; an NS record points to a name server with its domain name but IP address, so you need to assign a domain name at least for the name server.
Why the author didn't registered his own domain name, then? Because it has few advantages over many disadvantages.
sekiguchi.minamishinagawa.shinagawa.tokyo.jp. What a fascinating offer!There are some disadvantages as well.
The author's bootleg environment is operated as follows:
The author's base domain name is home.example.com.
The domain example.com is reserved to be used in manuals or other documents as an example. (See RFC 2606 for details.) So, this name will never be allocated for a real domain. If, as an accident, this domain name leaked, possible confusion will be minimum, since administrators know any use of this name indicates a bad configuration.
Actual hosts are allocated under a subdomain home.example.com. The reason is to minimize the chance of NS record conflict. example.com is a reserved domain, but there is a real NS record distributed on the Internet. The name server pointed to by the record is also real. (Any other record than the NS and mandatory SOA is not distributed.) When running a nameserver for the bootleg LAN, we need an NS record pointing to the server. If we used example.com directly, the NS record will be for example.com, and it may conflict with the real NS record for example.com when, for whatever reason, the in-house nameserver received the RR for registered example.com. If we allocate a subdomain, home.example.com, the NS record for the bootleg LAN is to home.example.com, and there are no chance of conflict, since there are no RR on the Internet for home.example.com.
When running a bootleg, you need an in-house DNS nameserver. Usual configuration/management tips for DNS servers for registered domain apply, but there are some special considerations.
See the following pages for configuration examples.