loopback address

This loopback address is also used for management datagrams, such as alarms, originating from the equipment.

This example only contains entries for the loopback addresses of the system and their host names, a typical default content of the file.

The resolution of the name 'localhost' to the most-commonly used loopback addresses is set up by the following lines in each device's hosts file:

So reserving its highest possible network number (127) for loopback testing eventually morphed into an excessive reservation of 16,777,214 loopback addresses.

By assigning the loopback address to each known ad server, the user directs traffic intended to reach each ad server to the local machine.

Programs can resolve that hostname to such a loopback address themselves, or pass it to the host's address resolution APIs.

The processing of any packets sent to a loopback address is implemented in the link-layer of the TCP/IP stack.

In the unicast addressing class, link-local addresses and the loopback address have link-local scope, which means they are to be used in the directly attached network (link).

The solution is to run a nameserver locally that can be queried over the IPv4 loopback address, but that turned out to be easier said than done.

An IPv4 or IPv6 address query for the name localhost must always resolve to the respective loopback address, which is specified in a separate standard.

Null routes are typically configured with a special route flag, but can also be implemented by forwarding packets to an illegal IP address such as 0.0.0.0, or the loopback address.

The IPv4 loopback addresses are separately reserved within the IPv4 namespace by the current IETF standard ().

In contrast, the current IETF standard () reserves a single IPv6 loopback address within the IPv6 namespace.

Any IP datagram with a source or destination address set to a loopback address must not appear outside of a computing system, or be routed by any routing device.

Localhost can also be mapped to other IPv4 loopback addresses, and additional synonyms can be assigned to any loopback address.

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.

If any such server does receive such a request, it should immediately return the appropriate loopback address (A or AAAA record request), or a negative response to any other request.

On most computer systems, localhost resolves to the address 127.0.0.1, which is the most-commonly used IPv4 loopback address, and to the IPv6 loopback address ::1.

When a device's hostname resolver receives a query for localhost, it should return the appropriate loopback addresses for A and AAAA record requests, and negative responses for any other requested records.

When using localhost from a client program (e.g., a PHP application), the MySQL application programming interface connects to the database using a Unix domain socket, while a TCP connection via the loopback address requires the direct use of the address.