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TOPIC: what is device loopback interface ?

what is device loopback interface ? 10 years 9 months ago #26823

Hi All,

Can anyone clearly explain what is a loopback interface in a network device ?.
what is the use of loopback interface ?

please provide some links if you found on this topic.

Thanks in Advance,

Re: what is device loopback interface ? 10 years 9 months ago #26826

  • S0lo
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It's a virtual (none-physical) interface. Basically a way of accessing the device itself without sending a signal out a physical interface.

It's useful in some situations. For example, In OSPF routing (were a router ID is defined as the highest IP value of all interfaces), it's useful to define a "loop back" interface and assign it a very high IP, to make sure that the router always has this defined ID no matter what physical interfaces are up or down.

An other use, is when certain software defines a "loop back interface" on a PC. For example VMware does similar things to allow virtual machines to communicate together all inside the PC.

On any PC, the IP is defined as a default loop back interface. successfully pinging this is typically used to ensure that the TCP/IP stack is working correctly.

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