IP addresses provide a method to uniquely identify every system connected to a network. Public IP addresses are routable over the Internet while private IP addresses may only be used on local area networks. Learn how IP addresses are assigned and managed.
- [Instructor] For the internet protocol to successfully deliver traffic between any two systems on a network, it must have an addressing scheme. Just like telephones use phone numbers, and postal mail uses street addresses, the internet needs an addressing scheme. Because the addresses are used by the internet protocol, they're known as IP addresses. In most cases, IP addresses are written in what's known as the dotted quad notation. This means that they are four numbers separated by periods.
Each number may range between zero and 255. Why 255? Because each number is represented using eight binary bits, and those bits can represent two to the eighth power possible numbers. Two to the eighth is 256, but since we start counting at zero, we can only go up to 255 in our IP address values. A system's IP address uniquely identifies it on a network. If the system is directly connected to the internet, the IP address it uses must not be used by any other system in the world, just as your mobile phone number is not used elsewhere in the world.
Systems that are connected to private networks, such as the one in your home or office, may use private IP addresses that are reusable on other networks. Your router or firewall takes care of translating those addresses to public IP addresses when you communicate over the internet using a protocol known as network address translation, or NAT. Don't worry about public or private IP addresses, or NAT, for now. We'll get back to them later. IP addresses are divided in two parts.
The network portion of the address identifies the network a system is connected to. Your company for example may have its own network address. The second portion of the address, the Host Address, uniquely identifies a system on that network. In this example, the network address is 192.168, and the host address is 1.100. The dividing line is right in the middle of the address, but it doesn't have to be. Some IP addresses have the dividing line here, or here, and you can even divide networks into smaller pieces than that.
We'll cover that more when we discuss subnetting later in this course. There are two IP addresses involved in every network communication. The source address indicates the system sending information, and the destination address indicates the system receiving information. As two systems communicate back and forth, the source and destination addresses will swap places, depending upon who sends each packet. IP addresses that use the dotted quad notation are part of the fourth version of IP, known as IPv4.
Unfortunately the world is running out of possible addresses in the IPv4 space, so we are shifting to a new standard known as IPv6. Unlike the 32 bit IPv4 addresses, IPv6 addresses use 128 bits, allowing for many more possible addresses. IPv6 addresses are written in hexadecimal notation, using eight groups of four hexadecimal digits, such as the address shown here. IP addresses are one of the core concepts in computer networking, and are critical to many security tasks.
Learn about communication and networking best practices, including TCP/IP networking, network security devices, and secure network design and management. Instructor and cybersecurity expert Mike Chapple also includes coverage of converged protocols, network encryption, and wireless networking. You can find Mike's companion study books for this series at the Sybex test prep site and review the complete CISSP Body of Knowledge at https://www.isc2.org/cissp-domains/default.aspx.
- IP addressing
- Switches and routers
- Content distribution networks
- Designing secure networks
- Specialized networking
- Managing secure networks
- Working with virtualized networks like SDNs
- Detecting and preventing network attaches
- Transport encryption
- Wireless networking
- Host security