If you live in a country like mine, where most networks are not publicly routable, you’ve probably given your LANs whimsical names so that they don’t have any chance of colliding with “real” domains on the internet. Of course, if you’re not pedantic (like me) you don’t bother to setup a DNS server since the network is not accessible from the outside anyway. However, for the few of you who do setup DNS servers on your local area networks I have one request. PLEASE PLEASE PLEASE do not use a .local top-level domain. I use .lan, and so should you.
The .local domain is what is called a pseudo-top-level domain. What does that mean? It means that it’s not an official top level domain usable (routable) on the internet, but it has a semi-official standing because it is used in some applications. In the case of .local it is used by the Multicast Domain Name Service (mDNS). Hosts that implement this service use .local as their domain names and have their own way of resolving names. Normally, this wouldn’t be a problem; however, if you also implement DNS on your network with .local as the top-level domain it will cause serious name resolution issues. I’ve seen this happen a lot on Linux systems, and I imagine Apple’s OS X will probably have these issues as well. Usually, on these types of networks you find that DNS name resolution doesn’t work at all or works only some of the time. In the end, you end up having to use ip addresses all the time because you don’t know whether a name might resolve or not (which negates the whole point of having a DNS server in the first place).
So, instead of naming your PCs server.mycompany.local, boss.mycompany.local, and sec.mycompany.local, use server.mycompany.lan, boss.mycompany.lan, and sec.mycompany.lan. I’ve been doing it for many years and haven’t had any problems.
P.S. – Please, also make sure to turn recursion off on your DNS server so that you don’t clog the internetz with spurious DNS requests for hosts on your internal domain.