IPv4 Address and Packet Basics

About this interactive

An IPv4 address is 32 bits, split into four 8-bit octets and written in dotted decimal, such as 192.168.0.42. Eight bits give 2^8 = 256 values, so each octet runs from 0 to 255; a number like 256 or 300 cannot fit in an octet, and an address that holds one is not a valid IPv4 address. Thirty-two bits give 2^32 = 4,294,967,296 addresses, about 4.3 billion. Data crosses a network in packets. Each packet starts with a header, at least 20 bytes (160 bits) in IPv4, and two of its fields are addresses. The destination address is where the packet is going: every router on the way reads it to choose the next hop. The source address is where it came from, and it is what makes a reply possible, because the reply swaps the two: the request's source becomes the reply's destination. Who a packet is for gives its delivery type. Unicast is one sender to one receiver. Broadcast is a packet addressed to every device on the local network. Multicast is one sender to a group: only the devices that joined that group process it. Addresses are handed out down a hierarchy. IANA, the Internet Assigned Numbers Authority, gives large blocks to the regional internet registries; they give smaller blocks to internet service providers (ISPs); and an ISP assigns addresses to its customers. The same hierarchy keeps routing manageable, because a block of addresses sits in one known place. Type numbers in digits and addresses in dotted decimal. Where an item asks for a word, the item names the choices. Capital letters do not matter. Anything you miss shows the answer and why. Seven of the nineteen items are drawn each run, so a second run is a different sheet.

What you'll learn

Apply the size rules of an IPv4 address: 8 bits and 256 values (0 to 255) to an octet, four octets and 32 bits to the address, about 4.3 billion addresses in all
Say which address goes in a packet's source field and which in its destination field, for a request and for the reply to it
Name a packet's delivery type, unicast, broadcast or multicast, from who it is sent to
Trace how address blocks are handed down: IANA to the regional internet registries, then to ISPs, then to their customers

Aligned to

CompTIA Network+

1.7 Given a scenario, use appropriate IPv4 network addressing.

Cisco CCNA

1.6 Configure and verify IPv4 addressing and subnetting

Cisco CCST Networking

2.2 Identify IPv4 addresses and subnet formats

4.4 Explain basic routing concepts

Key terms

Octet: One of the four 8-bit sections of an IPv4 address, each separated by a dot in dotted decimal notation and representing a decimal value from 0 to 255. For example, in 192.168.1.1, the four octets are 192, 168, 1, and 1.
IPv4: The fourth version of the Internet Protocol, using 32-bit addresses that provide approximately 4.3 billion unique addresses.
Dotted Decimal Notation: The standard human-readable format for representing IPv4 addresses as four decimal numbers (octets) separated by periods, such as 192.168.1.1. Each decimal value represents one 8-bit octet of the 32-bit IPv4 address.
Packet Header: The portion of a packet prepended to the payload that contains routing information, including source and destination IP addresses.
Unicast: A transmission type in which a packet is sent from one source directly to one specific destination device, identified by its unique IP or MAC address. Unicast is the standard delivery method for most internet traffic such as web browsing and file downloads.
Broadcast: A transmission type in which one device sends a single packet that is delivered to every other device on the local network segment simultaneously. Broadcast traffic is contained within a broadcast domain and does not cross router boundaries.
Multicast: A transmission type in which data is sent from one source to a specific group of devices that have subscribed to a multicast group address, rather than to all devices or just one. This differs from broadcast (all devices) and unicast (one device).
Hierarchical Addressing: An addressing scheme that organizes IP addresses into structured levels, enabling efficient routing and delegated administration of address ranges.
Internet Assigned Numbers Authority: The organization responsible for coordinating global IP addressing, port number assignments, and other internet protocol resources.
Internet Service Provider: A company that provides end users with access to the internet by connecting them to the internet backbone.

Topics

Ipv4 Octet Packet Header Unicast Broadcast Multicast Interactive Fill In

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