IP address

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

An IP address is a network-layer identifier assigned to a host or interface for packet delivery across interconnected networks.

An IP address is a Layer 3 identifier used to address packets to their final destination host across interconnected networks. Unlike a MAC address, which changes at each hop to identify the next device, the destination IP address remains the same throughout the journey. IPv4 and IPv6 are the two IP versions in use; they use different address formats. section 4.3.1 section 4.4

IPv4 addresses provide the practical foundation for understanding IP addressing:

• Represent each host at Layer 3 with a 32-bit number written as four 8-bit octets in dotted-decimal notation, such as 192.168.100.100. section 7.3 section 7.3.1
• Divide into a network portion and a host portion; the prefix length, such as /24, states how many bits belong to the network. section 7.3.1
• Group hosts on the same LAN under a shared network portion while assigning each host a unique host portion. section 7.3.1
• Enable routers to make forwarding decisions from destination IP addresses; routers need an appropriate address on each interface connecting a network. section 7.3 section 7.3.2

Assigning IPv4 addresses to a Cisco router

Before configuration, use `show ip interface brief` to check the current state. Enter interface configuration mode, assign an address and netmask, and enable the interface: `R1(config)# interface gigabitethernet0/0` `R1(config-if)# ip address 192.168.1.1 255.255.255.0` `R1(config-if)# no shutdown` Configure G0/1 similarly with `192.168.2.1 255.255.255.0`. Verify the result with `show ip interface brief`; both interfaces should display their addresses and an `up/up` status. section 7.3.2

Figure 4.3 TCP/IP Layer 3. PC1 addresses a message to SRV1’s IP address. Layer 3 is responsible for the end-to-end delivery of the message, whereas Layer 2 is responsible for the hop-to-hop delivery. The destination MAC address of the message changes at each hop, but the destination IP address remains the same throughout the journey.

Trace how a packet keeps its destination IP address while its destination MAC address changes at every hop. section 4.3.1

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

How deep it goes

Explains IPv4 structure, prefix lengths, router assignment, and verification, while deferring packet forwarding details.

Examples

Uses PC-to-server delivery, two LANs joined by a router, IPv4 notation, and Cisco interface configuration output.

What you can do after

Apply IPv4 addressing by configuring Cisco router interfaces and verifying their operational status.

How it connects

Connects IP addresses with TCP/IP layers, MAC addresses, routers, IPv4, IPv6, subnet masks, and prefix lengths.

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Related concepts

• domain name systemproduced by · The Domain Name System is a distributed, hierarchical naming system that resolves domain names to IP addresses and other network resource records.
• routerused by · A router is a network device that forwards packets between networks based on destination addresses and routing information.
• mac addresscontrasts with · A MAC address is a link-layer identifier assigned to a network interface for communication over a local network link.
• INET data typeused by · INET is a database data type for storing IPv4 and IPv6 host addresses.
• arpused by · The Address Resolution Protocol is a local-network protocol that maps an IPv4 address to the corresponding link-layer address, typically a MAC 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.