If you find yourself faced with a network topology that's changed enormously since the last time you surveyed it, or one which isn't correctly documented, don't despair.
Instead of auditing every machine in the network by hand and building a map of it, a more efficient and less time-consuming solution is using a program such as NetworkView (http://www.networkview.com) to build a map of the network automatically.
NetworkView queries a range of TCP/IP addresses on a given subnet and attempts to discover as much as possible about all the machines that respond to pings in that subnet. By default, the program will query for information via NetBIOS, SNMP, WMI and also attempt to determine which of a number of common TCP ports the machine is listening on (ftp, telnet, http, plus custom ports).
The discovery process can take a while for a fairly large or complex network, so it's best to let this stage run while you're doing other things and come back to it later.
Once the network discovery is finished, the program prints out a graphical chart of the network's topology. Each node in the network can have its details customized, and the results can be displayed in a variety of ways -- for instance, sorted by MAC address rather than IP address. The program can also be set to monitor nodes for changes, so the map is kept live at all times. If a node is offline during discovery, the user can add a node and set its details manually. NetworkView can also be set to alert an administrator in the event certain conditions change on the network (if a specific machine goes offline, for example).
Note that you should not use NetworkView on any network where you are not expressly authorized to do port scans of the machines on the network. This can be considered illegal in some jurisdictions.
(The cost for a single personal license is $79, which lets you use the product on several machines and on any network you choose, according to the company.)
Serdar Yegulalp is the editor of the Windows 2000 Power Users Newsletter. Check out his Windows 2000 blog for his latest advice and musings on the world of Windows network administrators -- please share your thoughts as well!