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IP Addresses, Subnet Masks, and Default Gateways

One of the most basic concepts of data networking is how devices connect and communicate within an IPv4 network. To understand this, we must look at the devices' unique IP addresses as well as the associated subnet mask and default gateway. With these three pieces of information, we know how a device communicates with others locally as well as across an entire network. In this article, I'll explain each aspect of a device's IP address configuration and how they work together in order to communicate with other devices on a network.

IP addresses

Easily the most widely understood component of the TCP/IP configuration is the IP address. 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. The difference is that it consists of four segments called octets that are separated by a period. The numbers within each octet range between 0 and 255. Here's an example of a typical IPv4 address:

No other device on your network -- unless you are using NAT -- will have the same IP address. Therefore,  for a device to communicate with another, the sending device must know the location of the destination before it can begin transmitting data. Depending on the locations of the source and destination devices as they relate to the subnet mask, the process of discovering the location of the destination device address will vary.

NEXT page: Subnet masks

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