1.7b - IPv4 Addressing (Prof. Messer)

Fundamental concepts of IPv4 addressing, including address structure, automated addressing like DHCP and APIPA, and RFC 1918 private address ranges.

IPv4 Address

A unique identifier that every device on a network must have to communicate, consisting of a series of four numbers separated by a period, such as $192.168.1.165$.

Subnet Mask

A $4$-octet value, such as $255.255.255.0$, used by a local device to determine which devices are on the local IP subnet and which are outside of it.

Default Gateway

The IP address of a device on the local subnet that allows communication outside of that subnet, typically assigned to a router by a network administrator.

Loopback Address

A range of addresses between $127.0.0.1$ through $127.255.255.254$ used to define the local device and confirm the local IP stack is working properly.

Reserved Addresses

A range of addresses from $240.0.0.1$ through $254.255.255.254$, including Class E addresses, set aside for future use or testing.

Virtual IP Address (VIP)

An IP address not associated with a physical Ethernet adapter, instead assigned to internal device components like a virtual machine or a router interior.

Octet

A group of $8$ individual bits; an IPv4 address is composed of $4$ octets, totaling $32$ bits or $4$ bytes.

$$255$$

The maximum decimal value possible for any individual octet in an IPv4 address, as each group consists of $8$ bits.

DHCP

Dynamic Host Configuration Protocol; a protocol that automatically assigns IP address configuration settings to devices when they connect to a network.

Link-local Address

An IP address that can only communicate to other devices on the same local subnet and cannot be used to route traffic outside of that subnet to the internet.

APIPA

Automatic Private IP Addressing; a process that automatically assigns a link-local address in the range of $169.254.0.1$ through $169.254.255.254$ if no DHCP server is available.

Private IP Address Range

Specific blocks of IPv4 addresses defined by RFC $1918$ that can only be used on internal networks and cannot be routed on the public internet.

Network Address Translation (NAT)

A functionality that allows the conversion of a private IP address into a public IP address to enable communication on the public network.

RFC $1918$ Class A Private Range

The address range from $10.0.0.0$ through $10.255.255.255$, represented in CIDR as $10.0.0.0/8$ with a host ID size of $24$ bits.

RFC $1918$ Class B Private Range

A block of $16$ contiguous class B ranges from $172.16.0.0$ through $172.31.255.255$, represented as $172.16.0.0/12$ with a host ID size of $20$ bits.

RFC $1918$ Class C Private Range

A block of $256$ contiguous class C ranges from $192.168.0.0$ through $192.168.255.255$, represented as $192.168.0.0/16$ with a host ID size of $16$ bits.