IS103 Lesson 3: Internet Protocol Version 4 (IPv4 Address)

Vocabulary flashcards covering the structure, classifications, special address ranges, subnetting formulas, and core terminology of IPv4 networking from IS103 Lesson 3.

IPv4 Address

A 32-bit logical address composed of exactly 32 binary bits, providing a theoretical capacity of approximately 4.3 billion addresses.

Octet

One of four 8-bit sections of an IPv4 address, separated from each other by decimal dots.

Dotted Decimal Notation

A human-readable format where the 32 binary bits of an IPv4 address are converted into four decimal numbers ranging from $0$ to $255$ per octet.

Network Portion

The component of an IPv4 address that identifies the specific physical or logical network segment; shared by all devices residing on the same local network.

Host Portion

The component of an IPv4 address that identifies a specific end device (such as a PC, server, or router interface) within a network segment; must be unique within that network.

Subnet Mask

A 32-bit value that uses consecutive 1s to highlight the network bits and consecutive 0s to highlight the host bits of an IP address.

Unicast

A one-to-one communication method where a data packet is transmitted from a single source host to one specific destination host.

Broadcast

A one-to-all communication method where a data packet is delivered to all active hosts located within the local subnet segment.

Multicast

A one-to-many communication method where a data packet is sent to a selected group of interested hosts within the $224.0.0.0/4$ range.

Public IP Addresses

Globally unique IP addresses that are routable across the public Internet and assigned by IANA and Regional Internet Registries (RIRs).

Private IP Addresses (RFC 1918)

Non-routable IP addresses over the public Internet that are reserved strictly for local internal networks (LANs).

Static IP Address

An IP address that is permanently fixed and manually configured on a device.

Dynamic IP Address

An IP address that is automatically assigned to a device (e.g., via DHCP) and can change periodically.

Class A Address

A classful IPv4 range with a first octet of $1-127$, a default mask of $255.0.0.0$ ($/8$), an 8 net / 24 host split, designed for huge organizations with up to 16 million hosts.

Class B Address

A classful IPv4 range with a first octet of $128-191$, a default mask of $255.255.0.0$ ($/16$), a 16 net / 16 host split, targeted for medium networks with up to 65k hosts.

Class C Address

A classful IPv4 range with a first octet of $192-223$, a default mask of $255.255.255.0$ ($/24$), a 24 net / 8 host split, targeted for small networks with up to 254 hosts.

Class D Address

A classful IPv4 range spanning first octets $224-239$ with no default subnet mask or net/host split, reserved specifically for multicast streaming groups.

Class E Address

A classful IPv4 range spanning first octets $240-255$ with no default subnet mask or net/host split, set aside for experimental and research/development purposes.

RFC 1918 Class A Private Range

The address block $10.0.0.0/8$ ($10.0.0.0 - 10.255.255.255$), primarily utilized for large enterprise corporate networks.

RFC 1918 Class B Private Range

The address block $172.16.0.0/12$ ($172.16.0.0 - 172.31.255.255$), primarily utilized for medium-sized business networks and subnets.

RFC 1918 Class C Private Range

The address block $192.168.0.0/16$ ($192.168.0.0 - 192.168.255.255$), primarily utilized for small office and home routers (SOHO LANs).

Classless Inter-Domain Routing (CIDR / RFC 1519)

An IP allocation method using variable-length prefix notation (e.g., $/24$, $/26$) that replaced rigid classful boundaries to prevent address exhaustion and allow customized subnet sizing.

Unspecified Address (0.0.0.0)

A special-use IPv4 address used by hosts as a temporary source IP during startup and bootstrapping prior to receiving an address via DHCP.

Limited Broadcast (255.255.255.255)

A broadcast address used to send messages to all hosts on the local physical network segment; traffic destined to this address is blocked by routers.

Loopback Address (127.0.0.0/8)

A reserved IPv4 range (commonly $127.0.0.1$) used for internal software testing where network traffic never leaves the host's internal network interface card (NIC) stack.

Automatic Private IP Addressing (APIPA / 169.254.0.0/16)

A link-local address range ($169.254.x.x$) auto-assigned by the operating system when a device cannot contact a DHCP server, supporting local segment connectivity only.

Total Subnets Formula

$2^n$, where $n$ represents the number of borrowed network bits from the host portion.

Usable Hosts Formula

$2^h - 2$, where $h$ represents the remaining host bits ($32 - \text{Prefix}$), subtracting 2 for the reserved Network ID and Broadcast ID.

Block Size

The total number of IP addresses contained within a subnet block, calculated as $2^h$, where $h$ is the number of host bits.

Network ID

The very first address in a subnet block that represents and identifies the subnet itself, and cannot be assigned to an individual host.

Broadcast ID

The final address in a subnet block that is reserved for transmitting data simultaneously to all hosts within that subnet.

Internet Assigned Numbers Authority (IANA)

The global governing body responsible for overseeing the allocation of global IP address blocks and coordinating with Regional Internet Registries (RIRs).

Network Address Translation (NAT)

A networking method that translates private IP addresses from an internal network into a single globally routable public IP address for internet communication.