Editing Private network (section)

==Link-local addresses==
{{main article|Link-local address}}

Another type of private networking uses the link-local address range. The validity of link-local addresses is limited to a single link; e.g. to all computers connected to a [[Network switch|switch]], or to one [[wireless network]]. Hosts on different sides of a [[network bridge]] are also on the same link, whereas hosts on different sides of a [[network router]] are on different links.

===IPv4===
In [[IPv4]], the utility of link-local addresses is in [[zero-configuration networking]] when [[Dynamic Host Configuration Protocol]] (DHCP) services are not available and manual configuration by a network administrator is not desirable. The block {{IPaddr|169.254.0.0|16}} was allocated for this purpose.{{Ref RFC|6890}}{{Ref RFC|3927}} If a host on an IEEE 802 ([[Ethernet]]) network cannot obtain a network address via DHCP, an address from {{IPaddr|169.254.1.0}} to {{IPaddr|169.254.254.255}}{{refn|group="Note"|The first and last {{IPaddr||24}} subranges of the subnet (addresses {{IPaddr|169.254.0.0}} through {{IPaddr|169.254.0.255}} and {{IPaddr|169.254.255.0}} through {{IPaddr|169.254.255.255}}) are reserved for future use.{{Ref RFC|3927|rsection=2.1}}}} may be assigned [[pseudorandom]]ly. The standard prescribes that address collisions must be handled gracefully.

===IPv6===
In [[IPv6]], the block {{IPaddr|fe80::|10}} is reserved for IP address autoconfiguration.{{Ref RFC|4291}}
The implementation of these link-local addresses is mandatory, as various functions of the IPv6 protocol depend on them.{{Ref RFC|4862}}

===Loopback interface===
A special case of private link-local addresses is the [[Loopback#Virtual loopback interface|loopback interface]]. These addresses are private and link-local by definition since packets never leave the host device.

IPv4 reserves the entire class A address block {{IPaddr|127.0.0.0|8}} for use as private loopback addresses. IPv6 reserves the single address {{IPaddr|::1}}.

Some are advocating reducing {{IPaddr|127.0.0.0|8}} to {{IPaddr|127.0.0.0|16}}.<ref>{{Cite IETF|draft=draft-schoen-intarea-unicast-127-06}}</ref>