127 loopback address question

Question

till which layer the loopback packet goes . i mean to ask that the lowest layer till which packet travel and then come back. I read that it goes to data link layer . but is the point to send it to data link layer as the address 127 is know at the network layer. at the same page i also read that it will return as the address 127 will be known . which is know at network layer . so i m confussed  till which point the packet will go .

Answer 1

127:x:X:x is an ip adddres where x cannot be simantously 0s and 1 all at once used for self connectivity (if internet is not working )

we send an ip with destination 127.x.x.x it goes to DATA LL and comes back to NETWOK LAYER

if it comes back then we can say no fault in our internet ascpects that support in our system

Comments

i think this is not hard coded . it is software based implementation .i just want to know how data link layer will know packet should be send up instead of up. if u have learned computer network and then u may be knowing every decision a layer takes is from seeing it's header or the upper layer data packet.

u just send me a proof or a link where it is writen it goes to data link layer. i will accept

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actully i have a friend who work in cisco company from past 10 years he answerd

i have googled enough but cannot find a link

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i have a teacher who works in cisco company and has a all india rank of 13 he answered it dll . and then during teaching he also told once it will go up through network layer. at that time i just missed it and now its creating problem . i think it should be n/w layer till a gud logic arrives

Answer 2

Only till DLL. DLL sends it back.

Comments

May be this is the case or the Network layer passes this information as an overhead to DLL which is higly unlikely because it will generate useless traffic.

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may be i think i should leave the reason . but r us sure it goes till data link layer . going to put it on stck overflow, will post if got an answer.

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It goes till DLL, am sure about that. It's better you ask the reason on Stack Overflow.

Answer 3

yap .it is dll sure. i feel as 127.x.x.x is a special address with this special property .. i dont know about technicality

Answer 4

It should return from Network Layer of the host in my opinion, however i was'nt able to find exact answer to this question .

 

Why do we have the Loopback address and why is it 127.0.0.1??? Early on when the Department of Defense in the US was designing TCP/IP, they decided that they should reserve a portion of the space for testing. They rather randomly selected the 127 space for this purpose. In fact - it is the entire space 127 space that they reserved. Many do not realize this, since the most common implementation is to assign 127.0.0.1. So try pinging the address 127.1.2.3 on your PC and it might just respond if your vendor supports testing with other numbers in the reserved loopback space.

 

What is the fact that your machine responds to 127.0.0.1 really telling you???

This is telling you that TCP/IP is properly initialized on your device. You might not have external interfaces set up properly,but the TCP/IP stack is indeed there and it is functional once you do the remaining required configurations.

 

Notice the creators of TCP/IP had no idea there would be an IP address shortage when they selected this space! They sure wasted a lot of addresses for this testing purpose.

 

Remember also that you can create your own loopback interfaces on Cisco devices. For example, you can do this:

 

interface loopback 101

ip address 10.10.10.1 255.255.255.0

 

This creates a virtual interface on your device that you can use for a wide variety of purposes - like testing a feature!

reference:https://learningnetwork.cisco.com/thread/52391