Hairpinning


In network computing, hairpinning describes a communication between two hosts behind the same NAT device using their mapped endpoint. Because not all NAT devices support this communication configuration, applications must be aware of it.
Hairpinning is where a machine on the LAN is able to access another machine on the LAN via the external IP address of the LAN/router.

Example

Consider a private network with the following:
If the NAT device supports hairpinning, then P1 application can connect to the P2 application using the external endpoint 203.0.113.54:5555.
If not, the communication will not work.