Loopback interfaces

What Are Loopback Interfaces and why we use loopback interfaces in OSPF routing protocol:

Loopback interfaces are logical interfaces, which are virtual, software-only interfaces; they are not real router interfaces.

In networking, we create Loopback interfaces on the router which serves in many ways. Loopback interfaces never go down until and unless the administrator intentionally shutdown it. Loopback interfaces do not require any type of medium eg. ethernet cables to connect so it is always up by default after creating a loopback interface in global configuration mode.

Loopback Interfaces play a major role in the OSPF routing protocol. Using loopback interfaces with your OSPF configuration ensures that an interface is always active for OSPF processes. They can be used for diagnostic purposes as well as OSPF configuration. the highest Loopback interface is selected as Router ID in OSPF if we have not configures any manual id on the interface.

In Computer, The Loopback Interfaces is a virtual network that your computer uses to communicate with itself. It is used mainly for troubleshooting and to connect to servers running on the local machine. The loopback IP address is 127.0.0.1.

with the Help of loopback interface address i.e 127.0.0.1, you can troubleshoot and ensure during network issue as a primary troubleshooting step that everything is fine and working at your Machine end i.e your ethernet adapter is working or not before going to troubleshoot on another device.

For IPv4, the loopback interfaces is assigned all the IPs in the 127.0.0.0/8 address block. That is, 127.0.0.1 through 127.255.255.254 all represent your computer. For most purposes, though, it is only necessary to use one IP address, and that is 127.0.0.1. This IP has the hostname of localhost mapped to it.

For Self Testing follow the steps:

Open CMD as Administrator

Type ping 127.0.0.1

Make sure the host is not connected to any of the networks.