Private network: Difference between revisions
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In the [[Internet]] addressing architecture, a '''private network''' is a network that uses private [[IP address]] space, following the standards set by RFC 1918 and RFC 4193. These addresses are commonly used for home, office, and enterprise [[local area network]]s (LANs), when globally routable addresses are not mandatory, or are not available for the either by accident, or from malicious traffic using a spoofed source address. Less commonly, ISP edge routers will drop such egress traffic from customers, which reduces the impact to the Internet of such misconfigured or malicious hosts on the customer's network. |
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==Private IPv4 address spaces== |
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The [[Internet Engineering Task Force]] (IETF) has directed the [[Internet Assigned Numbers Authority]] (IANA) to reserve the following IPv4 address ranges for private networks, as published in RFC 1918: |
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{| class="wikitable" |
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! RFC1918 name !! IP address range !! number of addresses |
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! ''[[classful network|classful]]'' description !! largest [[Classless Inter-Domain Routing|CIDR]] block (subnet mask) || host id size |
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|- |
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[[Classful addressing]] is obsolete and has not been used in the Internet since the implementation of [[Classless Inter-Domain Routing]] (CIDR) starting in 1993. For example, while 10.0.0.0/8 was a single class A network, it is common for organizations to divide it into smaller /16 or /24 networks. |
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==Private IPv6 addresses== |
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The concept of private networks and special address reservation for such networks has been carried over to the next generation of the [[Internet Protocol]], [[IPv6]]. |
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The address block <tt>fc00::/7</tt> has been reserved by IANA as described in RFC 4193. These addresses are called [[Unique Local Address]]es (ULA). They are defined as being [[unicast]] in character and contain a 40-bit random number in the routing prefix to prevent collisions when two private networks are interconnected. Despite being inherently ''local'' in usage, the IPv6 address scope of unique local addresses is global (cf. [[IPv6 address]]es, section "IPv6 Address Scopes"). |
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A former standard proposed the use of so-called "site-local" addresses in the fec0::/10 range, but due to major concerns about scalability and the poor definition of what constitutes a ''site'', its use has been deprecated since September 2004 by RFC 3879. |
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==Link-local addresses== |
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{{main|Zero configuration networking}} |
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{{also|Link-local address}} |
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Another type of private networking uses the ''link-local address range'' codified in RFC 5735 and RFC 3927. The utility of these addresses is in self-autoconfiguration by network devices when [[Dynamic Host Configuration Protocol]] (DHCP) services are not available and manual configuration by a network administrator is not desirable. |
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In IPv4, the block 169.254/16 is reserved for this purpose, with the exception of the first and the last /24 subnet in the range. If a host on an IEEE 802 ([[ethernet]]) network cannot obtain a network address via DHCP, an address from 169.254.1.0 to 169.254.254.255 may be assigned [[pseudorandom]]ly. The standard prescribes that address collisions must be handled gracefully. |
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The [[IPv6]] addressing architecture sets aside the block <tt>fe80::/10</tt> for IP address autoconfiguration. |
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Link-local addresses have even more restrictive rules than the private network addresses defined in RFC 1918: packets to or from link-local addresses must not be allowed to pass through a router. (RFC 3927, [http://tools.ietf.org/html/rfc3927#section-7 section 7]). |
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==Private use of other reserved addresses== |
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Historically other address blocks than the private address ranges have been reserved for other potential future uses. Some organizations have used them for private networking applications despite official warnings of possible future address collisions. |
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==RFC References== |
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* RFC 1918 – ''"Address Allocation for Private Internets"'' |
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* RFC 2036 – ''"Observations on the use of Components of the Class A Address Space within the Internet"'' |
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* RFC 2050 – ''"Internet Registry IP Allocation Guidelines"'' |
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* RFC 2101 – ''"IPv4 Address Behaviour Today"'' |
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* RFC 2663 – ''"IP Network Address Translator (NAT) Terminology and Considerations"'' |
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* RFC 3022 – ''"Traditional IP Network Address Translator (Traditional NAT)"'' |
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* RFC 3330 – ''"Special-Use IPv4 Addresses"'' (superseded) |
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* RFC 5735 – ''"Special-Use IPv4 Addresses"'' |
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* RFC 3879 – ''"Deprecating Site Local Addresses"'' |
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* RFC 3927 – ''"Dynamic Configuration of IPv4 Link-Local Addresses"'' |
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* RFC 4193 – ''"Unique Local IPv6 Unicast Addresses"'' |
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==References== |
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{{reflist}} |
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[[Category:Internet architecture]] |
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[[Category:Network_addressing]] |
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[[bg:Персонална мрежа]] |
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[[de:Private IP-Adresse]] |
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[[es:Red privada]] |
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[[fr:RFC 1918]] |
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[[it:Indirizzo IP privato]] |
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[[ja:プライベートネットワーク]] |
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[[nl:RFC 1918]] |
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[[no:Private IP-adresser]] |
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[[pt:Rede privada]] |
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[[sr:Приватна мрежа]] |
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Revision as of 18:58, 23 March 2010
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