Illustrated TCP/IP by Matthew G. Naugle Wiley Computer Publishing, John Wiley & Sons, Inc. ISBN: 0471196568   Pub Date: 11/01/98

Chapter 235
Address Records

The following indicates the name-to-IP-address mappings:

This file has new types: A (address) and CNAME (canonical name). The A record type stands for Address (A for 32-bit address, and AAAA for IPv6 addresses). There can be more than one address for a name, as in the case of a multihomed host (a host with a connection to more than one subnet). This could be stated as:

Name servers will return the closest address to the requester, depending on the requester’s address. If they are on the same network, the name server will place the closest address first. Since the DNS has no idea of route tables, if the requester and its network address are different, it will return both addresses. With each subsequent address, it will reverse the IP addresses in the response to provide some balance.

Aliases are just that, a name for another name. When a request comes in and the server finds a CNAME record, it replaces the name with the CNAME. It will then do another lookup, find the address, and return this to the requester.