Internet Protocol version 4 (IPv4)¶

Advantages of IPv4¶

• Universality: supported by every network device and application globally.

• Simplicity: mature and well-understood, with extensive troubleshooting tools.

• NAT (Network Address Translation): conserves public addresses and adds a layer of privacy.

• Broadcast Support: built-in mechanism for network-wide announcements.

Writing IPv4 addresses¶

• Dotted-Decimal Notation: four 8-bit octets separated by dots (e.g., 192.168.1.1).

• CIDR Notation: always include prefix length (e.g., 192.168.1.0/24).

• Private Address Ranges:

  • 10.0.0.0/8

  • 172.16.0.0/12

  • 192.168.0.0/16

• Avoid Leading Zeros: write 192.168.1.1, not 192.168.001.001.

IPv4 address types and scopes¶

Calculating IPv4 subnets¶

• Subnetting borrows bits from the host portion to create subnets.

• Formula: Number of subnets = 2^(borrowed_bits)

• Hosts per subnet = 2^(remaining_host_bits) - 2 (subtract network and broadcast).

• Example: subnet 192.168.1.0/24 into four /26 subnets:

  • Borrowed bits: 26 - 24 = 2 → 2^2 = 4 subnets.

  • Subnets: 192.168.1.0/26, .64/26, .128/26, .192/26.

  • Hosts per subnet: 2^(6) - 2 = 62.

Key IPv4-related protocols¶

• ARP (Address Resolution Protocol): maps IP addresses to MAC addresses.

• DHCP (Dynamic Host Configuration): assigns IP addresses and configs to hosts.

• ICMP (Internet Control Message Protocol): error reporting and diagnostics (e.g., ping).

• NAT (Network Address Translation): translates private IPs to public IPs.

• DNS (Domain Name System): resolves domain names to IP addresses.

Characteristics and security concerns¶

• Characteristics:

  • Uses broadcast for network-wide communication.

  • Relies on NAT for address conservation.

  • Header includes checksum for error detection.

• Security Concerns:

  • NAT Limitations: breaks end-to-end connectivity, complicating applications like VoIP.

  • ARP Spoofing: attackers poison ARP tables to intercept traffic.

  • Broadcast Storms: misconfigurations can lead to network congestion.

  • Address Exhaustion: limited address space (4.3 billion addresses) has been depleted.

  • Fragmentation Attacks: maliciously crafted packets can evade security controls.

IPv4 transition mechanisms to IPv6¶

• Dual Stack: devices run both IPv4 and IPv6 simultaneously.

• Tunnelling: encapsulate IPv6 in IPv4 packets (e.g., 6to4, Teredo).

• Translation: convert IPv4 to IPv6 (e.g., NAT64 with DNS64).

• Proxying: use a proxy to mediate between IPv4 and IPv6 hosts.

Quick Reference¶

• /24: common subnet mask for small networks (254 hosts).

• /30: typical for point-to-point links (2 hosts).

• Private Ranges: use 10.0.0.0/8 for large networks, 192.168.0.0/16 for home networks.

• NAT: essential for connecting private networks to the internet.