Use the PING utility between RADIUS components, such as your client and your RADIUS servers, to determine if there are network problems between different components of the system. If a ping by hostname succeeds, you have verified basic network functionality between the two servers. If a ping by hostname fails, try a ping by IP address.
PING returns the IP address of your hostname, number of bytes read, time to read packet, and time to live packet. PING will return an error result if it fails to connect to the server. This usually indicates a network or DNS problem between the computer running PING and the computer being pinged.
See your Windows NT documentation for information about arguments to the PING command.