IPv4 Address Cheat Sheet

An IP address cheat sheet can be handy for quick reference. Here’s a cheat sheet covering IPv4 addresses:

IPv4 Address Format

  • Representation:
    • Written in dotted-decimal format (e.g., 192.168.1.1).

IPv4 Address Types

  • Public Address:
    • Routable on the global Internet.
    • Example: Assigned by Internet service providers.
  • Private Address:
    • Used within private networks.
    • Ranges:
      • Class A: 10.0.0.0 to 10.255.255.255
      • Class B: 172.16.0.0 to 172.31.255.255
      • Class C: 192.168.0.0 to 192.168.255.255

IPv4 Subnet Mask

  • Representation:
    • Written in dotted-decimal format (e.g., 255.255.255.0).
  • CIDR Notation:
    • Written using the slash followed by the subnet prefix length (e.g., 192.168.1.0/24).

IPv4 Classes

  • Class A:
    • Range: 1.0.0.0 to 126.255.255.255
    • Subnet mask: 255.0.0.0
  • Class B:
    • Range: 128.0.0.0 to 191.255.255.255
    • Subnet mask: 255.255.0.0
  • Class C:
    • Range: 192.0.0.0 to 223.255.255.255
    • Subnet mask: 255.255.255.0

Special IP Addresses

  • Loopback Address:
    • 127.0.0.1 is reserved for testing purposes.
  • APIPA (Automatic Private IP Addressing):
    • 169.254.x.x is self-assigned by devices in the absence of DHCP.
  • Broadcast Addresses:
    • Broadcast addresses end with all host bits set to 1.
    • Example: Subnet 192.168.1.0/24 has a broadcast address of 192.168.1.255.

Reserved IP Addresses

  • Documentation Addresses:
    • 192.0.2.0 to 192.0.2.255 are reserved for documentation and examples.
  • Multicast Addresses:
    • Ranges 224.0.0.0 to 239.255.255.255 are reserved for multicast groups.

IP Address Notation Rules

  • Decimal Notation:
    • Each octet is a decimal number between 0 and 255.
  • Leading Zeros:
    • Leading zeros in each octet can be omitted.

IP Address Tools

  • IPv4 Calculators:
    • Various online tools available for subnetting and calculating IP addresses.

Best Practices

  • Use CIDR Notation:
    • Preferred for expressing IP address ranges and subnets.
  • Keep Documentation:
    • Maintain detailed documentation of IP address assignments.

Troubleshooting Tips

  • Check Subnet Mask:
    • Ensure that devices on the same network have the correct subnet mask.
  • Verify Default Gateway:
    • Confirm that devices have the correct default gateway for routing.

This cheat sheet provides a quick reference for understanding and working with IPv4 addresses, covering basic concepts and best practices.