Loopback

An RS-232 Transceiver can use loopback for testing its functionality. For example, a device's ''transmit'' pin connected to its ''receive'' pin will result in the device receiving exactly what it transmits. Moving this looping connection to the remote end of a cable adds the cable to this test. Moving it to the far end of a modem link extends the test further. This is a common troubleshooting technique and is often combined with a specialized test device that sends specific patterns and counts any errors that come back (see Bit Error Rate Tester ( BERT ) ). Some devices include built-in loopback capability.

. The standard Domain Name for this address is '' Localhost ''. A loopback interface is a type of 'circuitless IP address' or ' Virtual IP ' address, as the IP address is not associated with any one particular interface (or circuit) on the host or router.

On Unix -like systems, the loopback interface is commonly called lo or lo0.

A loopback interface has several uses. It may be used by network client software on a computer to communicate with server software on the same computer–viz., on a computer running a the loopback interface is a basic test that one's IP stack is working properly.

Loopback addresses are the subject of a reasonably common Internet -pings the loopback address. The only effect is a busy processor.

Packets sent on a "real" IP network with a source address on the loopback interface can cause a number of problems for older or buggy network software. Such packets are known as ''" Martian Packet s"''. {Link without Title}

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Loopback