IPv4 Addressing

Question 1

IPv4 Address

Answer 1

Made of four octets, also called four bytes or 32 bits; each octet can range from 0 to 255, with 255 being the highest decimal value per byte.

A unique 32-bit numerical identifier assigned to each device on a network, used for sending and receiving data between hosts.

Question 2

Subnet Mask

Answer 2

Subnet Mask → A 32-bit number that divides an IP address into network and host portions, determining which part identifies the network and which identifies the device.

An IP address consists of two parts: the network portion and the host portion. The subnet mask indicates which part is the network by masking the network bits with 1’s and the host bits with 0’s.

Class A Range: Used for large organizations
Subnet Mask = 255.0.0.0 (/8)
Can have 16 million+ hosts

Class B Range: Used for medium organizations
Subnet Mask = 255.240.0.0 (/12)
Can have 1 million+ hosts

Class C Range: Used for small organizations or home setup
Subnet Mask = 255.255.255.0 (/24)
Can have 254 hosts

Question 3

Default Gateway

Answer 3

Default Gateway → The router or device that connects a local network to external networks, acting as the exit point for traffic destined outside the local subnet.

Question 4

Loopback Address

Answer 4

Loopback Address → A special address used for internal network testing and troubleshooting, typically 127.0.0.1, which directs traffic back to the same device.

Question 5

Reserved Addresses

Answer 5

Reserved Addresses → A group of IP ranges not used for standard network communication, including the Class E range 240.0.0.0 to 255.255.255.254 reserved for experimental use.

Question 6

VIP

Answer 6

Virtual IP Address → An IP address assigned to multiple servers or services for redundancy and load balancing, allowing failover without changing client configurations.

Question 7

DHCP

Answer 7

Dynamic Host Configuration Protocol → Automatically assigns IP addresses, subnet masks, default gateways, and DNS information to devices on a network.

Question 8

APIPA

Answer 8

Automatic Private IP Addressing → A link-local address range (169.254.0.1 to 169.254.255.254) assigned automatically when a DHCP server is unavailable; uses ARP to ensure the address isn’t already in use.

Question 9

Private IP Address Ranges

Answer 9

Only used internally, can’t access the internet. Needs to be turned into a public IP address through NAT.

Usually your router has a DHCP server built into it that automatically gives all your devices private IP addresses.

Class A Range: Used for large organizations
IP= 10.0.0.0-10.255.255.255
Subnet Mask= 255.0.0.0 (/8)

Class B Range: Used for medium organizations
IP= 172.16.0.0-172.31.255.255
Subnet Mask= 255.240.0.0 (/12)

Class C Range: Used for small organizations or home setup
IP= 192.168.0.0-192.168.255.255
Subnet Mask= 255.255.255.0 (/24)

Private IPs > Router (Default Gateway) > NAT > Public IP address > Internet

Question 10

Public IP Address

Answer 10

No duplicates in the world. Needed to connect to the internet. ISP assigns one to your router, which is how you connect to the internet.

Usually a router has a NAT built into it that converts all your devices private IP addresses into a shared public IP address.

Private IPs > Router (Default Gateway) > NAT > Public IP address > Internet

Question 11

NAT

Answer 11

Network Address Translation → A process that translates private IP addresses into a single public IP address for outbound internet communication, conserving address space and improving security.

Question 12

RFC 1918

Answer 12

Request for Comments 1918 → The standard document that defines the private IP address ranges for Class A, B, and C networks, ensuring these addresses are not routable on the public internet.