Every device connected to a network must have an unique IP address to differentiate it from the others. An IP address is similar to the unique telephone number on your home phone or mobile device. No other device on your network (unless you are using NAT) will have the same IP address. In order for a sending device to transmit data to a receiving device, the sender needs to know where the destination is. The destination will either be on the same subnetwork as the source, or on some other subnetwork. If the devices are in the same subnet, the mechanism used to determine the location of the destination device is the broadcast. But what happens if they are on different networks? This is where the default gateway comes into play. The default gateway is used as the destination of all traffic that is not on the same subnet.
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