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Terme informatique

Loopback Interface

A virtual network interface used to join the machine itself or provide a stable logical address.

Networking
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Simple definition

A virtual network interface used to join the machine itself or provide a stable logical address.

Technical definition

A loopback is not linked to a physical port. 127.0.0.1 is the most known local IPv4 closure address; on network equipment, other loopbacks can serve as stable identifiers.

What is it used for ?

Test the local IP stack and provide addresses independent of physical interfaces.

Practical example

A local web service can listen on 127.0.0.1 so that it can only be accessed from the server.

Common issues

  • Service listening only in loopback
  • Confusion between localhost and address LAN
  • Road to a missing loopback

IP address · Router · Network port

Key takeaway: This entry explains the general operation of the term. Exact settings may vary depending on software, vendors and environments.

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