Network - Loopback IP address (virtual IP, lo or lo0')

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The loopback IP address is the address used to access itself.

The IPv4 designated as the loopback address with the subnet mask .

A loopback interface is also known as a virtual IP, which does not associate with hardware interface.

  • On Linux systems, the loopback interface is commonly called lo or lo0.
  • The corresponding hostname for this interface is called localhost.


The loopback address is used to test network software:


A good example of this is to access the web server running on itself by using or http://localhost.

A loopback adapter is required then if:

  • You are installing on a DHCP computer, or
  • You are installing on a non-networked computer and plan to connect the computer to a network after installation.


Dynamic Host Configuration Protocol (DHCP) assigns dynamic IP addresses on a network. Dynamic addressing allows a computer to have a different IP address each time it connects to the network. In some cases, the IP address can change while the computer is still connected. You can have a mixture of static and dynamic IP addressing in a DHCP system.

In a DHCP setup, the software tracks IP addresses, which simplifies network administration. This lets you add a new computer to the network without having to manually assign that computer a unique IP address. However, before installing an application onto a computer that uses the DHCP protocol, you need to install a loopback adapter to assign a local IP address to that computer.

Documentation / Reference

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