The

Internet Protocol Version 4 Internet Protocol version 4 (IPv4) is the first version of the Internet Protocol (IP) as a standalone specification. It is one of the core protocols of standards-based internetworking methods in the Internet and other packet-switched networks ...

(IPv4) address can have multiple uses.

Uses

Official meaning and use

IANA The Internet Assigned Numbers Authority (IANA) is a standards organization that oversees global IP address allocation, autonomous system number allocation, root zone management in the Domain Name System (DNS), media types, and other Internet P ...

, who allocate IP addresses globally, have allocated the single IP address to section 3.2.1.3. It is named as "This host on this network". RFC 1122 refers to using the notation . It prohibits this as a destination address in

IPv4 Internet Protocol version 4 (IPv4) is the first version of the Internet Protocol (IP) as a standalone specification. It is one of the core protocols of standards-based internetworking methods in the Internet and other packet-switched networks. ...

and only allows it as a source address under specific circumstances. A host may use as its own source address in IP when it has not yet been assigned an address, such as when sending the initial ''DHCPDISCOVER'' packet when using

DHCP The Dynamic Host Configuration Protocol (DHCP) is a network management protocol used on Internet Protocol (IP) networks for automatically assigning IP addresses and other communication parameters to devices connected to the network using a clie ...

Operating system specific uses

Some

operating systems An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

have attributed special internal meanings to the address. These uses do not result in IPv4 packets containing and so are not governed by RFC 1122. These meanings may not be consistent between operating systems. In both Windows and Linux, when selecting which of a host's IP address to use as a source IP, a program may specify INADDR_ANY (). In Linux a program may specify as the remote address to connect to the current host (AKA

localhost In computer networking, localhost is a hostname that refers to the current computer used to access it. The name ''localhost'' is reserved for loopback purposes. It is used to access the network services that are running on the host via t ...

Other non-standard uses

Besides the use by operating systems internally, other uses have been attributed to the address. * A non-routable meta-address used to designate an invalid, unknown or non applicable target * The address a host assigns to itself when address request via DHCP has failed, provided the host's IP stack supports this. This usage has been replaced with the APIPA mechanism in modern operating systems. * A way to explicitly specify that the target is unavailable. * A way to route a request to a nonexistent target instead of the original target. Often used for adblocking purposes. This can conflict with OS specific behaviour.

Routing

In routing tables, can also appear in the gateway column. This indicates that the gateway to reach the corresponding destination subnet is unspecified. This generally means that no intermediate routing hops are necessary because the system is directly connected to the destination. The

CIDR notation Classless Inter-Domain Routing (CIDR ) is a method for allocating IP addresses for IP routing. The Internet Engineering Task Force introduced CIDR in 1993 to replace the previous classful network addressing architecture on the Internet. Its goal ...

defines an IP block containing all possible IP addresses. It is commonly used in routing to depict the

default route In computer networking, the default route is a configuration of the Internet Protocol (IP) that establishes a forwarding rule for packets when no specific address of a next-hop host is available from the routing table or other routing mechanism ...

as a destination

subnet A subnet, or subnetwork, is a logical subdivision of an IP network. Updated by RFC 6918. The practice of dividing a network into two or more networks is called subnetting. Computers that belong to the same subnet are addressed with an identica ...

. It matches all addresses in the IPv4 address space and is present on most hosts, directed towards a local router.

In IPv6

IPv6 Internet Protocol version 6 (IPv6) is the most recent version of the Internet Protocol (IP), the communication protocol, communications protocol that provides an identification and location system for computers on networks and routes traffic ...

, the all-zeros address is typically represented by (two colons), which is the short notation of . The IPv6 variant serves the same purpose as its IPv4 counterpart.

0.0.0.0 day exploit

In August 2024, researchers from Israeli cybersecurity firm Oligo announced that they had discovered a security flaw was being exploited, in which malicious requests from a target's web browser were allowed to reach any port of the address of their target, allowing the browser (and therefore the remote attacker) to access private resources. Depending on what software is configured to be listening, the attackers could exfiltrate internal company information or developer code, or issue any requests to the software's APIs.

References

Works cited

External links

* {{Ref RFC, 6890, ref=no Routing IP addresses 0 (number)