IPv4

As explained in Acing the CCNA Exam: Volume 1 Fundamentals and Protocols

An IPv4 address is a 32-bit network-layer address used to identify a source or destination in IPv4 communication.

IPv4 is a 32-bit Layer 3 address used to identify a host and address a message to its final destination. Routers use the destination IP address when making forwarding decisions, while switches use MAC addresses for next-hop delivery. section 7.3 section 4.3.1

IPv4 addresses are written in dotted decimal notation: four 8-bit octets separated by periods. A prefix length such as /24 identifies the network portion; the remaining bits identify the host portion. Hosts on the same LAN share the network portion but use distinct host portions. section 7.3.1

Use these distinctions when analyzing IPv4 communication:

• Keep the destination IP address aimed at the final host throughout delivery; expect the destination MAC address to change at each hop. section 10.0
• Treat the prefix length as the boundary between network and host portions; /24 leaves 8 host bits. section 7.3.1
• Relate IPv4 addressing to subnetting, routing, ARP, routers, switches, and the TCP/IP model. section 7.0 section 10.0

Two LANs connected by a router

Hosts in LAN 1 can use addresses beginning 192.168.1, while hosts in LAN 2 can use addresses beginning 192.168.2. When PC1 sends to PC3 at 192.168.3.11, the Layer 3 destination remains PC3, but each hop uses a new Layer 2 frame addressed to the next hop. section 7.3.1 section 10.0

Figure 7.7 An IPv4 address written in both dotted decimal and binary. The 32-bit address is split into four octets consisting of 8 bits each. The address is divided into two parts: the network portion and the host portion. The prefix length indicates the size of the network portion in bits, and the remainder is the host portion.

Use the diagram to see how a 32-bit IPv4 address divides into four octets and separates network and host portions through a prefix length. section 7.3.1

How Acing the CCNA Exam: Volume 1 Fundamentals and Protocols covers it

How deep it goes

Explains 32-bit structure, dotted decimal notation, prefix lengths, network and host portions, but defers detailed routing decisions and subnetting.

Examples

Uses dotted-decimal addresses, LAN examples, prefix lengths, and a PC1-to-PC3 packet journey across routers.

What it assumes

Builds from basic binary and decimal conversion while assuming familiarity with the TCP/IP model and Layer 2 switching context.

What you can do after

Apply IPv4 addressing by configuring and verifying addresses on Cisco routers and distinguishing network, host, and next-hop information.

How it connects

Connects IPv4 with IPv6, MAC addresses, Layer 2, routers, ARP, routing, subnetting, and the TCP/IP model.

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Also explained in

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  Regular Expression Puzzles and AI Coding AssistantsAn IPv4 address is a 32-bit Internet Protocol version 4 address conventionally written as four decimal components separated by periods.

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Related concepts

• public ip addressincludes · A public IPv4 address is a globally unique IPv4 network address routable on the public Internet and assigned to an internet-facing resource.
• private ipv4 addressincludes · A private IPv4 address is an address from a designated range intended for communication within private networks rather than direct routing on the public Internet.
• IPv6addressed by · IPv6 is the sixth version of the Internet Protocol, using 128-bit network addresses for packet-based communication.
• regular expressionaddressed by · A formal pattern notation that describes sets of strings and enables text to be matched, searched, extracted, or transformed.
• maximum transmission unituses · The maximum transmission unit is the largest packet size that a network interface or link can transmit without fragmentation.
• octethas part · An octet is a group of exactly eight bits, commonly representing one byte or one component of an IPv4 address.

This explainer was generated by Manning's knowledge graph from the text of Acing the CCNA Exam: Volume 1 Fundamentals and Protocols. The section links point to the parts of the book it draws on.