Internet Protocol Version 4 (IPv4)

IPv4 is the foundational Layer 3 protocol of the TCP/IP stack, responsible for logical addressing, routing, and packet delivery across networks. Although its address space is limited, it remains widely deployed across global networks.

Category

Description

Use Case

IPv4 Basics

Covers the core format, header structure, and key attributes of IPv4. 32-bit address space, connectionless operation, TTL, fragmentation.

LAN/WAN connectivity, internet communication

IP Routing Protocols

Routing protocols used to forward IPv4 packets dynamically across networks. Includes RIP, OSPF, EIGRP, IS-IS, and BGP.

Dynamic routing, inter-networking, internet backbone routing

IPv4 Addressing

How IPv4 addresses are structured, assigned, and translated. Unicast, multicast, broadcast, NAT, private ranges, CIDR.

Host identification, subnetting, address conservation

RFC: RFC 791

Main Features:

  • 32-bit addressing scheme in dotted-decimal format (e.g., 192.168.0.1)

  • Operates at OSI Layer 3 (Network Layer)

  • Provides logical addressing and packet fragmentation

  • Header includes TTL, checksum, protocol, and source/destination IP

  • Stateless and connectionless: each packet is treated independently

  • Widely deployed across all modern networks

Use Cases:

  • Core of internet communication

  • IP routing within and between enterprise networks

  • Host identification in TCP/IP model

Alternative Protocols:

  • IPv6 – Next-generation protocol with larger address space and security

  • IPX – Legacy Novell protocol (obsolete)

  • AppleTalk – Deprecated Apple protocol

Let us learn more about IPv4:

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RFCs: - RIP: RFC 1058 - OSPF: RFC 2328 - EIGRP: RFC 7868 - IS-IS: RFC 1142 - BGP: RFC 4271

Main Features:

  • Path determination and packet forwarding

  • RIP – Simple distance-vector protocol (max 15 hops)

  • OSPF – Link-state protocol, uses areas for large-scale deployment

  • EIGRP – Cisco hybrid protocol using DUAL

  • IS-IS – ISP-grade scalable protocol

  • BGP – Internet-wide inter-AS routing protocol, supports policy control

Use Cases:

  • Enterprise and service provider routing

  • Autonomous System (AS) interconnectivity

  • Dynamic topology awareness and failover

Alternative Protocols:

  • Static routing – Manually defined routes

  • IPv6 Routing Protocols – OSPFv3, MP-BGP, RIPng

Let us learn more about IP Routing Protocols for IPv4:

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RFCs: RFC 791, RFC 950, RFC 1918, RFC 3022

Main Features:

  • 32-bit address space with ~4.3 billion addresses

  • Address Types: - Unicast: one-to-one - Broadcast: one-to-all on subnet (255.255.255.255) - Multicast: Class D (224.0.0.0 – 239.255.255.255)

  • CIDR (Classless Inter-Domain Routing): /n format for flexible subnetting

  • Private Address Ranges: - 10.0.0.0/8 - 172.16.0.0/12 - 192.168.0.0/16

  • NAT: Translates private addresses to public for internet access

Use Cases:

  • Host IP allocation in enterprise and ISP networks

  • Internet access via NAT from private IPs

  • Network segmentation via subnetting

Alternative Protocols:

  • IPv6 – Uses 128-bit address space and does not require NAT

  • DHCP – For automatic IP address assignment

  • MAC – Layer 2 addressing (hardware level)

Let us learn more about IPv4 Addressing:

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