As a network consultant for a large number of clients, I am often asked to make changes in IP addressing on servers and workstations when installing new firewalls or broadband Internet connections. One of the easiest and most convenient ways I have found for recording existing IP addressing is via a simple command and redirection parameter.
In Windows 98/NT/2000, move to a command prompt and type "ipconfig /all > c:ipbefore.txt" (sans quotes).This will send the output containing the local host name, IP address, subnet mask, gateway, DNS entries, WINS servers, and DHCP server and lease, if applicable, to the file c:ipbefore.txt (any filename will work).
After I make the change to the IP schema, I repeat the command but direct it to c:ipafter.txt for documentation and future reference. I can also compare the two files to verify that the intended changes have occurred.
It's an easy command but proves useful for quick documentation and verification.
(It can even be scripted or enhanced via the ">>" redirection command to append the information to a common file on a network share i.e.: "ipconfig /all >> P:networkip.txt" This would append the local PC address information to the ip.txt file on the network share "P:" in the folder "network." A great way for maintaining informal documentation on smaller networks.)