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Automatic Private IP Addressing (APIPA)
Last updated: 10/19/01

Q.  What is Automatic Private IP Addressing (APIPA)?

A.  Windows 98, 98 SE, Me, and 2000 have an Automatic Private IP Addressing (APIPA) feature that will automatically assign an Internet Protocol address to a computer on which it installed.  This occurs when the TCP/IP protocol is installed, set to obtain it's IP address automatically from a Dynamic Host Configuration Protocol server,  and when there is no DHCP server present or the DHCP server is not available.  The Internet Assigned Numbers Authority (IANA) has reserved private IP addresses in the range of 169.254.0.0 -169.254.255.255 for Automatic Private IP Addressing.

After the network adapter has been assigned an automatic IP address, a computer can communicate with any other computers on the local network that are also configured by APIPA or have static IP address manually set to the 169.254.x.y (where x.y is the client's unique identifier) address range with a subnet mask of 255.255.0.0.

You may want to turn-off this feature if...

  • Your network uses routers, including broadband routers with built-in DHCP servers).
  • Your network is connected to the Internet without a NAT or proxy server.

Use Start, Run, enter winipcfg, select the adapter for Windows 98, 98 SE, Me to detect APIPA and to release and renew the automaitc IP when a DHCP server becomes available.  The windows 2000 equivalent is ipconfig.  Use Start, Run, enter cmd and then enter ipconfig at the command prompt.  Enter...

c:\>ipconfig /?

... to obtain a list of command options.

See Microsoft Knowledgebase Article Q220874, Automatic Windows 98/Me TCP/IP Addressing Without a DHCP Server for more information and how to turn-off this feature.

Larry

Copyright, Disclaimer, and Trademark Information Copyright © 1996-2006 Larry F. Byard.  All rights reserved. This material or parts thereof may not be copied, published, put on the Internet, rewritten, or redistributed without explicit, written permission from the author.