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What I found was loopback tests whether the TCP/IP suite of our system is working properly or not and pinging our IP makes sure that NIC is working fine. This is okay but I wish to know its working with respect to OSI reference model i.e., what are the layers that involved in this.

Thanks in advance.

Ramana Reddy
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3 Answers3

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When everything is working correctly, they should have the same effect.

The two are on different "interfaces" - the lookback address is on the loopback interface which should be present always (unless you've done something really freaky with your config). The local IP address is on one of your other network interfaces.

If that interface didn't come up, then that ping will fail but the loopback IP should still work.

Furthermore, depending on how your network interface is set up - specifically whether it's getting an auto IP address via something like DHCP, or whether you've given it a static IP - the interface might come up but not have the IP address you expect, in which case pinging the IP address will also fail.

thomasrutter
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  1. lo is the loop-back address and will respond whether the hardware works or not and does not get transported to the physical layer.

  2. Any other address will only respond if the actual hardware is working and connected so this will go to the physical layer.

  3. There is also a way to create a hardware loop-back address if you need it and that will go to the physical layer as well without testing the cabling part of the physical layer.

So layers go from transport to physical depending on the kind of address you ping.

Community
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Fabby
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There are 7 OSI layers: physical, datalink, network, transport, session, presentation and application layers.

So if my understanding is correct ( and please correct me if I am wrong, I do want to learn ), pinging loopback address tests the network card (physical layer), while pinging your own IP address or other IP addresses involves network layer. Pinging external ip addresses gets onto transport level and if we can surf internet with browser such as firefox that is already up in the application layer

Sergiy Kolodyazhnyy
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