Localhost is the term used in computer networking to refer to the IP address of the local computer. The localhost address physically refers to the network interface card’s loopback interface on the computer. The IP address for the localhost is 127.0.0.1 in the legacy IP v4 definition and is ::1 in the emerging IP v6 standard. The localhost IP address is used to conduct computer networking on a client computer using the loopback interface on a network interface card (NIC).
What is the Localhost Used For?
Use of the localhost is primarily geared for network and application testing on a computer. The localhost name or IP address is used in place of a live URL or IP address on the Internet and resolves to the client’s computer. For example, by entering “localhost” or “127.0.0.1” in the address bar of a web browser and any activated hosting services on the client computer will be visible. Some applications will make use of the localhost IP address in order to perform networking functions more efficiently if they do not require communication with a centralized web server.
What Are Differences in Localhost Implementation on IP V4 and IP V6?
In Ipv4, the 127.0.0.0/8 address block is reserved for use by the localhost and loopback applications or testing. When applications make use of the localhost for making use of this interface, they will normally use a subnet mask of 255.0.0.0 along with an IP address of 127.0.0.1. The routing table of the local computing system will be configured to route any network packets resolving to the 127.0.0.0/8 addresses to the loopback on the local NIC card.
IP V6, however, only defines one address as being associated with the local host, 0:0:0:0:0:0:0:1, or ::1. Additional IP addresses in IP V6 can be assigned to the localhost, however, if they appear outside of the local computing system. IP V6 routing rules require that these packets be dropped. Multicast datapackets will also be dropped when routed to the localhost and require a live network connection in order to perform application development testing.