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Link-local address

 
Computer Desktop Encyclopedia: link-local address
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An IP address in the range from 169.254.1.0 to 169.254.254.255. It is used to automatically assign an IP address to a device in an IP network when there is no other assignment method available, such as a DHCP server. After an address is chosen, the link-local process sends an ARP query with that IP onto the network to see if it exists. If there is no response, the IP is assigned to the device, otherwise another IP is selected, and the ARP is repeated. See ARP, DHCP, Zeroconf and UPnP.

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Wikipedia: Link-local address
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Link-local addresses are network addresses which are intended only for communications within one segment of a local network (a link) or a point-to-point connection. They allow addressing hosts without using a globally-routable address prefix. Routers will not forward packets with link-local addresses.

Link-local addresses are often used for network address configuration when no external source of network addressing information is available. This addressing is accomplished by the host operating system using a process known as stateless address autoconfiguration. This is possible in both IPv4 and IPv6.

IPv4 addresses in the range 169.254.0.0/16 are assigned automatically by a host operating system when no other IP addressing assignment is available, e.g., from a DHCP server. In IPv6, link-local addresses are required and are automatically chosen with the FE80::/10 prefix.

Contents

IPv4

Based on RFC 3927, IPv4 uses the 169.254.0.0/16 (169.254.0.0 to 169.254.255.255) range of addresses for link-local addressing.[1] The document refers to the technique as IPv4 Link-Local (IPV4LL). Microsoft refers to this as Automatic Private IP Addressing (APIPA) or Internet Protocol Automatic Configuration (IPAC).

IPv6

IPv6 hosts automatically assign each of their interfaces a unique address based on the IEEE 802 MAC address. This autoconfiguration is specified in RFC 4862.[2] A link-local unicast address has the prefix FE80::/10 in standard IPv6 CIDR notation or 1111111010 in binary.[3]

IPv6 hosts usually have more than one address assigned to each of their network interfaces. The link-local address is required for IPv6 operation and additional addresses are global and/or private (unique local, ULA) in scope. Both global and private addresses can be assigned by automatic (stateless) or stateful (DHCPv6) mechanisms.

See also

References

  1. ^ RFC 3927, Dynamic Configuration of IPv4 Link-Local Addresses, S. Cheshire, B. Aboba, E. Guttman, The Internet Society (May 2005)
  2. ^ RFC 4862, IPv6 Stateless Address Autoconfiguration, S. Thompson, T. Narten, T. Jinmei (September 2007)
  3. ^ RFC 4291, IP Version 6 Addressing Architecture - 2.4. Address Type Identification, R. Hinden, S. Deering, The Internet Society (February 2006)
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