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APIPA: Automatic Private IP Addressing

APIPA serves as a fail-safe during DHCP problems

By Bradley Mitchell Bradley Mitchell Writer Massachusetts Institute of Technology University of Illinois An MIT graduate who brings years of technical experience to articles on SEO, computers, and wireless networking. lifewire's editorial guidelines Updated on June 25, 2021 Tweet Share Email Tweet Share Email

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Expand Jump to a Section How APIPA Works Configuration Limitations Automatic Private IP Addressing (APIPA) is a DHCP fail-safe that protects a computer system from failure. It invokes a standby mechanism for local Internet Protocol version 4 (IPv4) networks supported by Microsoft Windows. With APIPA, DHCP clients can obtain IP addresses even when DHCP servers are not functional. APIPA exists in all modern versions of Windows, including Windows 10.

How APIPA Works

Networks that are set up for dynamic addressing rely on a DHCP server to manage the pool of available local IP addresses. When a Windows client device attempts to join the local network, it contacts the DHCP server to request its IP address. If the DHCP server stops functioning or a network glitch interferes with the request, this process can fail. When the DHCP process fails, Windows automatically assigns an IP address from the private range, which is 169.254.0.1 to 169.254.254.255. Using Address Resolution Protocol (ARP), clients verify that the chosen APIPA address is unique on the network before they use it. Clients then check with the DHCP server at periodic intervals—usually every five minutes—and update their addresses automatically when the DHCP server is able to service requests. When you start a computer that has Windows 10 installed, for example, it waits for a few seconds for a DHCP server before using an IP from the APIPA range. Earlier versions of Windows look for a DHCP server for as long as three minutes. All APIPA devices use the default network mask 255.255.0.0, and all reside on the same subnet.

APIPA Configuration

APIPA is enabled by default in Windows whenever the PC network interface is configured for DHCP. This option is called autoconfiguration in Windows utilities such as ipconfig. A computer administrator can disable the feature by editing the Windows Registry and setting the following key value to 0: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\
Parameters\Interfaces\{network interface ID}\
IPAutoconfigurationEnabled If IPAutoconfiguration Enabled isn't listed, then it is by default set to 1. Instead, add a new REG_DWORD and set it to 0. Failures in the DHCP process indicate network troubleshooting is needed to identify and resolve the issues that prevent DHCP from working properly.

Limitations of APIPA

APIPA addresses do not fall into any of the private IP address ranges defined by the Internet Protocol standard and are restricted for use on local networks only. Like private IP addresses, ping tests or other connection requests from the internet and other outside networks cannot be made to APIPA devices directly. APIPA-configured devices can communicate with peer devices on their local network but cannot communicate outside of the network. While APIPA provides Windows clients a usable IP address, it does not provide the client with nameserver (DNS or WINS) and network gateway addresses as DHCP does. Local networks should not attempt to manually assign addresses in the APIPA range because IP address conflicts will result. To maintain the benefit APIPA has of indicating DHCP failures, avoid using those addresses for any other purpose and instead limit networks to use the standard IP address ranges. Was this page helpful? Thanks for letting us know! Get the Latest Tech News Delivered Every Day Subscribe Tell us why! Other Not enough details Hard to understand Submit More from Lifewire Private IP Addresses: Everything You Need to Know How to Fix a 169 IP Address Error What Is an IP Address? NETGEAR Default Password List (Updated October 2022) How to Change DNS Servers in Windows What Is a Public IP Address? (and How to Find Yours) Cisco Default Password List (Updated October 2022) How to Use an IP Address to Find a MAC Address How to Find the Default IP Address of a Belkin Router What Is DHCP? (Dynamic Host Configuration Protocol) How to Look up an IP Address Owner When to Use a Static IP Address How to Connect Two Routers on a Home Network What Is the 10.1.1.1 IP Address? How to Change Your IP Address How to Set Up Port Forwarding Newsletter Sign Up Newsletter Sign Up Newsletter Sign Up Newsletter Sign Up Newsletter Sign Up By clicking “Accept All Cookies”, you agree to the storing of cookies on your device to enhance site navigation, analyze site usage, and assist in our marketing efforts. Cookies Settings Accept All Cookies