While this approach works for small LANs, it isn't very convenient for larger LANs with many systems on them. For such configurations, it's generally much better to store all your IP-to-hostname mapping information on a single machine, and set up what is called a "DNS server" (domain name service server) on it. Then, you can configure each machine to contact this particular machine to receive up-to-the-minute IP to name mappings. This is done by creating an /etc/resolv.conf file on every machine that looks something like this:

 
domain gentoo.org 
nameserver 192.168.1.1 
nameserver 192.168.1.2 

In the above /etc/resolv.conf, I tell the system that any host names that are not qualified (such as "testbox" as opposed to "testbox.gentoo.org," etc.) should be considered to be local hostnames. I also specify that I have a DNS server running on 192.168.1.1, as well as a backup one running on 192.168.12. Actually, nearly all network-connected Linux PCs already have a nameserver specified in their resolv.conf file, even if they aren't on a LAN. This is because they are configured to use a DNS server at their Internet Service Provider, in order to map hostnames to IP addresses (so that users on that system can do things like browse the Web and head over to well-known sites like ibm.com without having to refer to them by IP address!).