Internet Protocol Version 4 (IPv4)
==================================

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   IPv4/ipv4
   IPv4/IP_Routing_Protocols
   IPv4/IPv4_Addressing

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.

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   * - 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

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   .. tab-item:: IPv4 Basics

      **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

      .. panels::
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         :card: What You Will Learn in This Section

         **Let us learn more about IPv4:**

         * :ref:`Learnings in this section <IPv4_step1>`

         * :ref:`Terminology <IPv4_step2>`

         * :ref:`Version Info <IPv4_step3>`

         * :ref:`IPv4 Version&RFC Details <IPv4_step5>`

         * :ref:`IPv4 Basic Setup on Ubuntu using IPv4 <IPv4_step21>`

         * :ref:`IPv4 Basic Setup on Ubuntu using IPv6 <IPv4_step22>`

         * :ref:`IPv4 Protocol Packet Details <IPv4_step6>`

         * :ref:`IPv4 Usecases <IPv4_step7>`

         * :ref:`IPv4 Basic Features <IPv4_step8>`

         * :ref:`IPv4 Feature : Addressing <IPv4_step9>` 

         * :ref:`IPv4 Feature : Header Structure <IPv4_step10>`

         * :ref:`IPv4 Feature : Packet Routing <IPv4_step11>`  

         * :ref:`IPv4 Feature : Fragmentation <IPv4_step12>`  

         * :ref:`IPv4 Feature : Connectionless Protocol <IPv4_step13>`

         * :ref:`IPv4 Feature : Subnetting <IPv4_step14>`

         * :ref:`IPv4 Feature : NAT Compatibility <IPv4_step15>`   

         * :ref:`IPv4 Feature : Broadcast Support <IPv4_step16>` 

         * :ref:`IPv4 Feature : Protocol Identification <IPv4_step17>` 

         * :ref:`IPv4 Feature : TTL (Time to Live) <IPv4_step18>` 

         * :ref:`IPv4 Feature : Classful Addressing (Legacy) <IPv4_step19>` 

         * :ref:`Reference links <IPv4_step20>`

         .. button-link:: ./IPv4/ipv4.html
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            Jump to "IPv4 Basics"

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   .. tab-item:: IP Routing Protocols

      **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

      .. panels::
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         **Let us learn more about IP Routing Protocols for IPv4:**


         .. button-link:: ./IPv4/IP_Routing_Protocols.html
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            Jump to "IPv4 Routing Protocols"

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   .. tab-item:: IPv4 Addressing

      **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)

      .. panels::
         :container: container pb-4
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         :card: What You Will Learn in This Section

         **Let us learn more about IPv4 Addressing:**


         .. button-link:: ./IPv4/IPv4_Addressing.html
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            Jump to "IPv4 Addressing"