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IP in Practice: IP Addressing Basics

Whenever you order at a fast-food restaurant, the cashier may give you a number or ask for the name on your order. When your order is ready, they will call your number or name so the correct person receives it. Similarly, devices on a network are assigned a unique number so information reaches its intended destination. This number is called an IP address.

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IP Addresses are Unique Identifiers

Every device on a network has an IP address that allows it to communicate with other devices. These addresses are unique within a network to ensure data reaches its intended destination. Imagine if two people had the same order number—there would be confusion about who ordered what. Similarly, without these identifiers, devices would not know where to send or receive data.

Purposes of IP Addresses

IP addresses serve several purposes, including:

Routing: IP addresses operate at layer 3 of the TCP/IP or OSI model, also known as the Network Layer or Internet Layer. At this layer, devices can send data within LANs and across the internet. Unlike fixed MAC addresses, IP addresses are considered logical addresses because they can change depending on which network a device joins. For example, your MAC may remain the same, but your IP will likely change when you connect to a different network.

Identifying Source and Destination: When two devices communicate, the roles of sender and receiver alternate. An IP packet contains both the source and destination IP addresses so data is correctly routed between devices.

Location: An IP address can indicate the type of network a device is on or its general location. IP address ranges determine whether a network is private or public. Regional Internet registries allocate IP address space for specific regions, while IANA registers these large address blocks globally.

Types of IP Addresses

IP addresses can be grouped by:

Assignment

  • Dynamic IP addresses: Assigned by a DHCP server, which provides network details allowing devices to communicate with others. These addresses may change when joining different networks. Read more on DHCP.
  • Static IP addresses: Manually assigned. These can be reserved so certain devices maintain a consistent IP address for simplicity, convenience, and stability, such as servers, printers, and smart devices.

Communication Method

  • Unicast address: One-to-one communication between two devices. This is the most common type of network communication.
  • Broadcast address: One-to-all communication, sending data to every device on the network. These are often used in ARP requests to find a device's MAC address for a given IP.
  • Multicast address: One-to-many communication, sending data to multiple devices but not necessarily all devices on a network. This is common when casting a screen to several devices.

Scope

  • Private addresses: Defined in RFC1918. These addresses are used within LANs, such as at home or in organizations.
    • There are three ranges of private addresses:
      • Class A: 10.0.0.0 – 10.255.255.255
      • Class B: 172.16.0.0 – 172.31.255.255
      • Class C: 192.168.0.0 – 192.168.255.255
    • Private addresses are not globally routable and must be translated to access the internet.
  • Public addresses: Routable across the internet. Many websites and organizations use these addresses to allow users to access their services.

5 Myths

  • Myth: I should hide my IP address to stay safe online.

    Clarification: Public IP addresses are designed to be globally routable. Home networks use private IP addresses with a router using NAT (Network Address Translation). Each device accesses the internet through the router, which replaces private IP addresses with a public NAT address.

  • Myth: You must cover your IP address on screens.

    Clarification: In typical scenarios, only public IP addresses are exposed beyond a local network. Private addresses are not publicly routable, meaning they cannot be directly accessed from the internet without NAT traversal or physical network access.

  • Myth: Using a VPN hides my IP.

    Clarification: A VPN creates a private, encrypted connection over a public network. Your IP address does not disappear; it is masked by the VPN server’s IP address. Websites see the VPN’s IP address, while your original IP is hidden from them, though it may still be visible to your ISP or the VPN provider.

  • Myth: Never use public Wi-Fi.

    Clarification: Public Wi-Fi can pose risks due to weak or absent encryption. Older standards like WEP, WPA, and WPA2 had weaker protections. WPA2-Personal uses a shared key, which could allow traffic to be intercepted. WPA3 and Enhanced Open create unique keys per device, improving security. It’s generally a good practice to use a VPN, secure websites (HTTPS), and avoid transmitting sensitive information.

  • Myth: I am directly connected to the Internet.

    Clarification: In most home or business networks, devices are not directly public-facing. Routers often use NAT to allow multiple devices to share a single public IP address. NAT converts private IP addresses to a public address for internet access while keeping your network safer.

Next Part

IP addresses have two formats: IPv4 and IPv6. Now that we have covered the basics, let's take a deep dive into IPv4, understanding how it is structured and its types.

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