Networks

APIPA (Automatic Private IP Addressing)

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APIPA (Automatic Private IP Addressing) is a DHCP fail-over instrument used with IPv4 (Internet Protocol Version 4). APIPA is envisioned for use in non-routed business environments with less than 25 clients being ideal. It is supported by all modern versions of Microsoft Windows. By using APIPA, DHCP clients can gain IP addresses when DHCP servers are not working correctly. APIPA is enabled by default in Windows whenever a PC network interface is constructed for DHCP. It works very much like autoconfiguration/ipconfig. This feature can also be disabled by editing the registry. APIPA set-up devices can communicate with peer devices on their local network but not outside of its network. APIPA also does not provide clients with name-server or network gateway addresses like DHCP does.
APIPA works by selecting an IP address from an address range of 169.254.0.0 – 169.254.255.255 when DHCP is not available. However, a DHCP server can be added to the network without needing an APIPA-based configuration by using ARP (Address Resolution Protocol); the chosen address is made unique. APIPA also automatically checks for the presence of a DHCP server approximately every 5 minutes, according to Microsoft. If this process finds a DHCP server, the APOPA stops and then replaces the APIPA networking addresses with dynamic ones.
DHCP can suffer from multiple types of problems such as server failure or maintenance, failure of relay agents on the client’s local network, hardware malfunctions, power failures, and running out of ready-to-be allocated addresses. Because of these potential problems, APIPA is essential and has become a standard in the industry. However, many network administrators find APIPA to be not essential and even annoying when troubleshooting. For example, when you run IPCONFIG, it would at first appear that the client has an IP address, at least until you actually look at the numbers. Because of this, many decide to turn APIPA off. If APIPA is adequately configured though, one can reduce issues and increase productivity by lowering DHCP failure.
References:
Mitchel, Bradley. (24 Feb 2017). LifeWire. APIPA – Automatic Private IP Addressing. Retrieved from https://www.lifewire.com/automatic-private-internet-protocol-addressing-816437.

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