Link-Local Addressing – What is Link-Local Addressing?

ipip addressip-link-localipv4ipv6

I noticed that IPv4 reserved 169.254.0.0/16 and IPv6 reserved fe80::/10 for link-local addressing. While I saw IPv6 uses both fe80::/10 address and my private IPv6 address fd00::12 to communicate with other devices in Wireshark, I never seen 169.254/16 working in IPv4.

So, what is the purpose of link-local addressing?

Best Answer

I never seen 169.254/16 working in IPv4.

A PC automatically acquires a 169.254.x.x/16 address if it does not receive an IP address from a DHCP server. If you disable the DHCP server on your home or lab network and issue the "ipconfig/release" and "ipconfig/renew" commands, your PC will receive a 169.254.x.x address.

As per this article:

The purpose of these self-assigned link-local addresses is to facilitate communication with other hosts within the subnet even in the absence of external address configuration (via manual input or DHCP). Unlike in IPv6, implementation of IPv4 link-local addresses is recommended only in the absence of a normal, routable address. Hosts pseudo-randomly generate the last two octets of the address to mitigate address conflicts. Because of the broadcast nature of some local networking protocols (for example, Microsoft's NetBIOS), hosts may be able to detect one another even without any preexisting knowledge of the address scheme.

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