Ip Address And Subnet Mask

Subnet

IP address

Definition

An Internet Protocol address is a numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication. An IP address serves two main functions: host or network interface identification and location addressing. 

IP address stands for internet protocol address; it is an identifying number that is associated with a specific computer or computer network. When connected to the internet, the IP address allows the computers to send and receive information.

How do IP addresses work

If you want to understand why a particular device is not connecting in the way you would expect or you want to troubleshoot why your network may not be working, it helps understand how IP addresses work.

Internet Protocol works the same way as any other language, by communicating using set guidelines to pass information. All devices find, send, and exchange information with other connected devices using this protocol. By speaking the same language, any computer in any location can talk to one another.

The use of IP addresses typically happens behind the scenes. The process works like this:

  1. Your device indirectly connects to the internet by connecting at first to a network connected to the internet, which then grants your device access to the internet.
  2. When you are at home, that network will probably be your Internet Service Provider (ISP). At work, it will be your company network.
  3. Your IP address is assigned to your device by your ISP.
  4. Your internet activity goes through the ISP, and they route it back to you, using your IP address. Since they are giving you access to the internet, it is their role to assign an IP address to your device.
  5. However, your IP address can change. For example, turning your modem or router on or off can change it. Or you can contact your ISP, and they can change it for you.
  6. When you are out and about – for example, traveling – and you take your device with you, your home IP address does not come with you. This is because you will be using another network (Wi-Fi at a hotel, airport, or coffee shop, etc.) to access the internet and will be using a different (and temporary) IP address, assigned to you by the ISP of the hotel, airport or coffee shop.

As the process implies, there are different types of IP addresses, which we explore below.

Types of IP addresses

There are different categories of IP addresses, and within each category, different types.

Consumer IP addresses

Every individual or business with an internet service plan will have two types of IP addresses: their private IP addresses and their public IP address. The terms public and private relate to the network location — that is, a private IP address is used inside a network, while a public one is used outside a network.

Private IP addresses

Every device that connects to your internet network has a private IP address. This includes computers, smartphones, and tablets but also any Bluetooth-enabled devices like speakers, printers, or smart TVs. With the growing internet of things, the number of private IP addresses you have at home is probably growing. Your router needs a way to identify these items separately, and many items need a way to recognize each other. Therefore, your router generates private IP addresses that are unique identifiers for each device that differentiate them on the network.

Public IP addresses

A public IP address is the primary address associated with your whole network. While each connected device has its own IP address, they are also included within the main IP address for your network. As described above, your public IP address is provided to your router by your ISP. Typically, ISPs have a large pool of IP addresses that they distribute to their customers. Your public IP address is the address that all the devices outside your internet network will use to recognize your network.

Public IP addresses

Public IP addresses come in two forms – dynamic and static.

Dynamic IP addresses

Dynamic IP addresses change automatically and regularly. ISPs buy a large pool of IP addresses and assign them automatically to their customers. Periodically, they re-assign them and put the older IP addresses back into the pool to be used for other customers. The rationale for this approach is to generate cost savings for the ISP. Automating the regular movement of IP addresses means they don’t have to carry out specific actions to re-establish a customer’s IP address if they move home, for example. There are security benefits, too, because a changing IP address makes it harder for criminals to hack into your network interface.

Static IP addresses

In contrast to dynamic IP addresses, static addresses remain consistent. Once the network assigns an IP address, it remains the same. Most individuals and businesses do not need a static IP address, but for businesses that plan to host their own server, it is crucial to have one. This is because a static IP address ensures that websites and email addresses tied to it will have a consistent IP address — vital if you want other devices to be able to find them consistently on the web.

This leads to the next point – which is the two types of website IP addresses.

There are two types of website IP addresses

For website owners who don’t host their own server, and instead rely on a web hosting package – which is the case for most websites – there are two types of website IP addresses. These are shared and dedicated.

Shared IP addresses

Websites that rely on shared hosting plans from web hosting providers will typically be one of many websites hosted on the same server. This tends to be the case for individual websites or SME websites, where traffic volumes are manageable, and the sites themselves are limited in terms of the number of pages, etc. Websites hosted in this way will have shared IP addresses.

Dedicated IP addresses

Some web hosting plans have the option to purchase a dedicated IP address (or addresses). This can make obtaining an SSL certificate easier and allows you to run your own File Transfer Protocol (FTP) server. This makes it easier to share and transfer files with multiple people within an organization and allow anonymous FTP sharing options. A dedicated IP address also allows you to access your website using the IP address alone rather than the domain name — useful if you want to build and test it before registering your domain.

How to look up IP addresses

The simplest way to check your router’s public IP address is to search “What is my IP address?” on Google. Google will show you the answer at the top of the page.

Other websites will show you the same information: they can see your public IP address because, by visiting the site, your router has made a request and therefore revealed the information. Sites like WhatIsMyIP.com and IPLocation go further by showing the name of your ISP and your city.

Generally, you will only receive an approximation of location using this technique — where the provider is, but not the actual device location. If you are doing this, remember to log out of your VPN too. Obtaining the actual physical location address for the public IP address usually requires a search warrant to be submitted to the ISP.

Finding your private IP address varies by platform:

In Windows:

  • Use the command prompt.
  • Search for “cmd” (without the quotes) using Windows search
  • In the resulting pop-up box, type “ipconfig” (no quote marks) to find the information.

On a Mac:

  • Go to System Preferences
  • Select network – and the information should be visible.

On an iPhone:

  • Go to Settings
  • Select Wi-Fi and click the “i” in a circle () next to the network you are on – the IP address should be visible under the DHCP tab.

If you need to check the IP addresses of other devices on your network, go into the router. How you access the router depends on the brand and the software it uses. Generally, you should be able to type the router’s gateway IP address into a web browser on the same network to access it. From there, you will need to navigate to something like “attached devices,” which should display a list of all the devices currently or recently attached to the network — including their IP addresses.

Haven known about IP addresses, we will now discuss subnet mask

WHAT IS SUBNET MASK

A subnetwork or subnet is a logical subdivision of an IP network. The practice of dividing a network into two or more networks is called subnetting. Computers that belong to a subnet are addressed with an identical most-significant bit-group in their IP addresses.

A subnet mask is a 32-bit number created by setting host bits to all 0s and setting network bits to all 1s. In this way, the subnet mask separates the IP address into the network and host addresses.

The “255” address is always assigned to a broadcast address, and the “0” address is always assigned to a network address. Neither can be assigned to hosts, as they are reserved for these special purposes.

The IP address, subnet mask and gateway or router comprise an underlying structure—the Internet Protocol—that most networks use to facilitate inter-device communication.

When organizations need additional subnetworking, subnetting divides the host element of the IP address further into a subnet. The goal of subnet masks are simply to enable the subnetting process. The phrase “mask” is applied because the subnet mask essentially uses its own 32-bit number to mask the IP address.

IP Address and Subnet Mask

A 32-bit IP address uniquely identifies a single device on an IP network. The 32 binary bits are divided into the host and network sections by the subnet mask but they are also broken into four 8-bit octets.

Because binary is challenging, we convert each octet so they are expressed in dot decimal. This results in the characteristic dotted decimal format for IP addresses—for example, 172.16.254.1. The range of values in decimal is 0 to 255 because that represents 00000000 to 11111111 in binary.

IP Address Classes and Subnet Masks

Since the internet must accommodate networks of all sizes, an addressing scheme for a range of networks exists based on how the octets in an IP address are broken down. You can determine based on the three high-order or left-most bits in any given IP address which of the five different classes of networks, A to E, the address falls within.

(Class D networks are reserved for multicasting, and Class E networks not used on the internet because they are reserved for research by the Internet Engineering Task Force IETF.)

A Class A subnet mask reflects the network portion in the first octet and leaves octets 2, 3, and 4 for the network manager to divide into hosts and subnets as needed. Class A is for networks with more than 65,536 hosts.

A Class B subnet mask claims the first two octets for the network, leaving the remaining part of the address, the 16 bits of octets 3 and 4, for the subnet and host part. Class B is for networks with 256 to 65,534 hosts.

In a Class C subnet mask, the network portion is the first three octets with the hosts and subnets in just the remaining 8 bits of octet 4. Class C is for smaller networks with fewer than 254 hosts.

Class A, B, and C networks have natural masks, or default subnet masks:

  • Class A: 255.0.0.0
  • Class B: 255.255.0.0
  • Class C: 255.255.255.0

You can determine the number and type of IP addresses any given local network requires based on its default subnet mask.

An example of Class A IP address and subnet mask would be the Class A default submask of 255.0.0.0 and an IP address of 10.20.12.2.

How Does Subnetting Work?

Subnetting is the technique for logically partitioning a single physical network into multiple smaller sub-networks or subnets.

Subnetting enables an organization to conceal network complexity and reduce network traffic by adding subnets without a new network number. When a single network number must be used across many segments of a local area network (LAN), subnetting is essential.

The benefits of subnetting include:

  • Reducing broadcast volume and thus network traffic
  • Enabling work from home
  • Allowing organizations to surpass LAN constraints such as maximum number of hosts

Network Addressing

The standard modern network prefix, used for both IPv6 and IPv4, is Classless Inter-Domain Routing (CIDR) notation. IPv4 addresses represented in CIDR notation are called network masks, and they specify the number of bits in the prefix to the address after a forward slash (/) separator. This is the sole standards-based format in IPv6 to denote routing or network prefixes.

To assign an IP address to a network interface since the advent of CIDR, there are two parameters: a subnet mask and the address. Subnetting increases routing complexity, because there must be a separate entry in each connected router’s tables to represent each locally connected subnet.

What Is a Subnet Mask Calculator?

Some know how to calculate subnet masks by hand, but most use subnet mask calculators. There are several types of network subnet calculators. Some cover a wider range of functions and have greater scope, while others have specific utilities. These tools may provide information such as IP range, IP address, subnet mask, and network address.

Here are some of the most common varieties of IP subnet mask calculator:

  • A IPv6 IP Subnet Calculator maps hierarchical subnets.
  • An IPv4/IPv6 Calculator/Converter is an IP mask calculator that supports IPv6 alternative and condensed formats. This network subnet calculator may also allow you to convert IP numbers from IPv4 to IPv6.
  • An IPv4 CIDR Calculator is a subnet mask adjustment and Hex conversion tool.
  • An IPv4 Wildcard Calculator reveals which portions of an IP address are available for examination by calculating the IP address wildcard mask.
  • Use a HEX Subnet Calculator to calculate the first and last subnet addresses, including the hexadecimal notations of multicast addresses.
  • A simple IP Subnet Mask Calculator determines the smallest available corresponding subnet and subnet mask.
  • A Subnet Range/Address Range Calculator provides start and end addresses.

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