How does loopback address work?

@rahul69-97fAOs • Oct 14, 2024

Oct 14, 2024

1.2K

I want to know how the loopback address is actually implemented? That is, when we use loopback address (127.0.0.1), does a software runs which virtually mimics the network, or the packet actually goes into the network, and if it does, how does it returns back to the sender?

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Abhishek Rawal

@abhishek-fg9tRh • Mar 14, 2013

It is theoretically said that, loopback address is connected to "Loopback Interface" which is a virtual Network device, so it's not possible of transmission of packets.
No packets or data bytes goes out of your system, it is bounded to your system.

As far I know, Loopback interface (lo) is usually used to test client-server application in which both client & server are running on same machine.
Loopback Interface Network Device due to loopback address shows "always connected" thus testing is possible.
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durga ch

@durga-TpX3gO • Mar 14, 2013

A typical example where loopback IP is used is - to test the TCP IP stack in a specific machine.
Aka, when you ping an IP address, x.y.z.a , you are trying to reach the IP over a specific set of network.
When you are trying to access 127.0.0.1, you are just trying to access the local machine, Also its not a physical NIC card or an interface.
As per primitive internet standards (classfull addressing )Packets destined to 127.0.0.1 are not supposed to leave a specific network and is specifically reserved for localhost purposes
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