#Purpose of a loopback address software#

#Purpose of a loopback address software#

In the end, all of these virtual interfaces are created with software (and they basically modify/change the network packets that you send/receive - source IP, source MAC etc.) and they do in fact use the physical interfaces to communicate over a network. Bridge interfaces are virtual interfaces as well. Networking devices do have software installed on them, just like an operating system, and can create multiple types of virtual interfaces, among them being the loopback.īut there are other types of virtual interfaces, that have a different purpose (not for testing the network stack and sending traffic back or management), like the tunnel interfaces usually used for VPNs. It is also used by various routing protocols and other services. In networkingĪlso, (from ), you can see that the use for a loopback interface can actually be different in some cases, as in Networking (and networking devices as router/switches/firewalls, etc.) is mostly used as a management interface.

So pinging/sending traffic to 'localhost' is actually done using a loopback interface. The IPv4 address block 127.0.0.0/8 is actually reserved for this reason and usually the 'localhost' points to an address from that range. If you have 2 applications running on the same system and you want to test if they can communicate with each other via the network, you won't need a router/switch (or whatever else would constitute the network), you just use software and a couple of commands to create some loopback interfaces and you route traffic through those. So from my point of view, the main purpose of the loopback interface(s) is to have an easy way to test the network stack of your system. Any traffic that a computer program sends to a loopback IP address is simply and immediately passed back up the network software stack as if it had been received from another device. It is implemented entirely within the operating system's networking software and passes no packets to any network interface controller. Implementations of the Internet protocol suite include a virtual network interface through which network applications can communicate when executing on the same machine. To go over the basic meaning and utility of the loopback interface (from ) I guess you are moving a little bit too fast and mixing the terms a little.