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Automatic Private IP Addressing (APIPA) is Microsoft’s term for a Windows computer automatically choosing an IPv4 address in the 169.254.0.0–169.254.255.255 range when it is configured for DHCP but cannot obtain a valid address from a DHCP server. It can support communication with compatible devices on the same local link, but it is not a normal network address for reaching other subnets or the internet.
What does APIPA mean?
APIPA stands for Automatic Private IP Addressing. On Windows, it describes automatic fallback addressing: if a DHCP-configured computer cannot get a valid IPv4 address from a DHCP server, it can assign itself an address from the reserved 169.254 range. Microsoft describes the feature in its guide to automatic TCP/IP addressing without a DHCP server.
The broader standards term for this behavior is IPv4 link-local addressing. The IETF defines the 169.254/16 prefix for link-local configuration in RFC 3927, published in May 2005.
What does a 169.254.x.x address let a device do?
A link-local address is intended for communication between devices on the same physical or logical link. It does not provide ordinary routed access to other networks. Routers must not forward packets with a 169.254/16 source or destination address, so an APIPA address alone does not provide internet access through a router. The IETF describes the same-link scope in RFC 3927.
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Whether two devices can communicate locally also depends on their network configuration and connectivity. The address indicates a limited scope; it does not guarantee that every local service or device will be reachable.
How does APIPA differ from a DHCP address?
| Address type | Who assigns it | Intended scope | Can routers forward it? |
|---|---|---|---|
| APIPA / IPv4 link-local (169.254/16) | The device assigns itself when DHCP does not provide a valid IPv4 address. | Communication on the same physical or logical link. | No. Routers must not forward packets with a link-local source or destination address, under RFC 3927. |
| DHCP-assigned IPv4 address | A DHCP service supplies a lease through the DHCP exchange. | The configured network; ordinary access depends on the settings supplied and the network path. | Potentially, according to the network configuration. DHCP assignment itself does not guarantee internet access. |
Microsoft describes the DHCP client/server exchange as Discover, Offer, Request, and Acknowledgement in its DHCP troubleshooting guide. APIPA is not another DHCP lease: it is the client’s fallback when it lacks a valid DHCP-provided IPv4 address.
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Why might a computer receive an APIPA address?
A 169.254.x.x address is a clue that the computer did not obtain a valid IPv4 address through DHCP. It does not, by itself, identify the cause. The problem could be on the client, DHCP server, relay, or network path between them. Microsoft’s DHCP troubleshooting guidance treats APIPA as a possible result when a client has no valid IPv4 address, rather than proof of a specific failure.
On Windows, run ipconfig /all in Command Prompt to inspect the network configuration and whether autoconfiguration is active. Microsoft documents this check in its APIPA support guide. Use the result to confirm what address the adapter has; it does not determine which part of the DHCP path needs attention.
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Does APIPA check for duplicate addresses?
Yes. RFC 3927 requires implementations to anticipate address conflicts and handle a detected conflict by selecting a different address. The RFC also advises against manually assigning or distributing addresses from 169.254/16 through DHCP: doing so can bypass the special automatic configuration and conflict-detection behavior intended for link-local addresses.
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