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That means any packet sent to any of those addresses is looped back. The address 127.0.0.1 is the standard address for IPv4 loopback traffic; the rest are not supported by all operating systems. However, they can be used to set up multiple server applications on the host, all listening on the same port number.
Special address blocks Address block (CIDR) First address Last address Number of addresses Usage Purpose ::/128 :: :: 1 Software Unspecified address
RFC 1122 refers to 0.0.0.0 using the notation {0,0}. It prohibits this as a destination address in IPv4 and only allows it as a source address under specific circumstances. A host may use 0.0.0.0 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 name localhost is a commonly defined hostname for the loopback interface in most TCP/IP systems, resolving to the IP addresses 127.0.0.1 in IPv4 and ::1 for IPv6.As a top-level domain, the name has traditionally been defined statically in host DNS implementations with address records (A and AAAA) pointing to the same loopback addresses.
The Internet Engineering Task Force (IETF) has reserved the IPv4 address block 169.254.0.0 / 16 (169.254.0.0 – 169.254.255.255) for link-local addressing. [1] The entire range may be used for this purpose, except for the first 256 and last 256 addresses (169.254.0.0 / 24 and 169.254.255.0 / 24), which are reserved for future use and must not be selected by a host using this dynamic ...
127.0.0.1 localhost loopback ::1 localhost This example only contains entries for the loopback addresses of the system and their host names, a typical default content of the hosts file. The example illustrates that an IP address may have multiple host names ( localhost and loopback ), and that a host name may be mapped to both IPv4 and IPv6 IP ...
In contrast, a port which rejects connections or ignores all packets directed at it is called a closed port. [ 1 ] Ports are an integral part of the Internet's communication model — they are the channel through which applications on the client computer can reach the software on the server .
This is useful for determining the efficiency of a certain route from two points in a network. In this example, it is more efficient to communicate with the computer itself through the use of address 127.0.0.1 (called localhost) than it would be through 192.168.0.100 (the IP address of the local network card).