The loopback address for each machine is 127.0.0.1, regardless of how many machines are on the network.
11111111
127.0.0.1 is the standard IP address used for a loopback network connection.This means that if you try to connect to 127.0.0.1, you are immediately looped back to your own machine.
This IP address is usually called the localhost address.
LOOPBACK ADDRESS - 127.0.0.0\8 IP Network range is reserved for Internal Testing.
There are several IP addresses that are special in one way or another. These addresses are for special purposes or are to be put to special use.Addresses significant to every IP subnet Network AddressBroadcast AddressAddresses significant to individual hosts Loopback AddressSpecial Addresses of Global Significance Private AddressesReserved AddressesLOOPBACK ADDRESS (127.0.0.1)The 127.0.0.0 class 'A' subnet is used for only a single address: the loopback address 127.0.0.1. This address is used to test the local network interface device's functionality. All network interface devices should respond to this address. If you ping 127.0.0.1, you can be assured that the network hardware is functioning and that the network software is also functioning.
In a mobile network, a switch's loopback address is a configured logical address not associated with a physical interface. It's useful for routing as it's always up and operational unless otherwise manually brought down. Whereas a physical ip address can lose routing if the interface goes down or if it's handling significant amounts of traffic.
ping 127.0.0.1
Successfully pinging the loopback address verifies that TCP/IP is installed and configured correctly on the local client.
The loopback address is 127.0.0.1. It is also called 'localhost'. It's purpose is simple: It's the most rudimentary test for functionality of your NIC (Network Interface Card). For example, if you ping 127.0.0.1 OR ping localhost you'll get a response IF your NIC is enabled, connected to something (physical network or wireless) and working. Problems with localhost pinging usually means a problem with the NIC itself. Google Web Accelerator, Hello, and some other tools take advantage of the loopback address for functionality. They open a port on loopback to internally 'host' web pages. Google Web Accelerator for example, creates a local cache of your web pages, and sets your proxy to the loopback address on a specific port, so that you get the local cache first, giving the illusion of instantaneous loading of the page.
Loopback plug
Use the PING (and current IP address) command to execute a loopback test on a NIC
Your loop-back address or localhost is always 127.0.0.1. When a packet is sent to this address, the packet is routed internally to the network loopback device. The packet is then received back by your computer as if it came from an outside source.