From the course: CompTIA Security+ (SY0-601) Cert Prep: 8 Network Security Design and Implementation

IP addresses and DHCP

From the course: CompTIA Security+ (SY0-601) Cert Prep: 8 Network Security Design and Implementation

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IP addresses and DHCP

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- [Instructor] For the Internet Protocol to successfully deliver traffic between any two systems on a network, it has to use 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. IP addresses are written in what's known as the dotted quad notation. This means that they are four numbers separated by periods. Each of these numbers may range between zero and 255. Now, you might ask, why 255? That's because each number in the dotted quad notation 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 that 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 in other networks. Your router or firewall takes care of translating those addresses to public IP addresses when you communicate over the internet. This takes place using a protocol known as network address translation, or NAT. IP addresses are divided into two parts. The network portion of the address identifies the network that a system is connected to. Your company 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. This uses a concept called subnetting. 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're shifting to a new standard known as IPv6. Unlike the 32-bit IPv4 addresses, IPv6 addresses use 128 bits, allowing for many more addresses. IPv6 addresses are written in hexadecimal notation, using eight groups of four hexadecimal digits, such as the example shown here. IP addresses are one of the core concepts in computer networking, and they're critical to many security tasks. They may be assigned in two different ways. First, you can assign an IP address statically. This means that you go into the system's settings and manually specify its IP address. You'll then be responsible for ensuring that you choose a unique address that fits within the range for your network. Second, you can use the Dynamic Host Configuration Protocol, or DHCP. DHCP allows you to configure a pool of IP addresses, and then DHCP will automatically assign those addresses to systems as they join the network. Typically, servers are configured with static IP addresses, and end user devices are configured with dynamically changing IP addresses.

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