Networking › Module 2 › Lesson 1
IPv4 Addressing
Understand IPv4 format, dotted decimal notation, and what an IP address identifies
Opening
Every device on a network needs a name tag
Your laptop, phone, server, and router each need a unique identifier to send and receive data. In IPv4, that identifier is a 32-bit number written as four decimal octets—like 192.168.1.50. For security teams, IP addresses are the bread crumbs of an investigation: who connected, from where, and to what.
1. IPv4 Format — Dotted Decimal
An IPv4 address is 32 bits long, split into four groups of 8 bits called octets. Each octet ranges from 0 to 255. Humans write them separated by dots: 192.168.1.1 10.0.0.5 172.16.254.1 Behind the scenes, the network sees binary: 11000000.10101000.00000001.00000001
2. What an IP Address Identifies
A host on a network
The address belongs to one interface on one device—not the whole building, just that network connection.
Logical, not physical
Unlike a MAC address burned into a NIC, an IP can change. DHCP assigns addresses dynamically.
Network + host portion
Part of the address identifies the network; the rest identifies the specific host. Subnet masks define the split.
3. Special and Reserved Addresses
127.0.0.1 (loopback)
Traffic to yourself—used for local testing. Malware sometimes abuses loopback for local C2.
0.0.0.0
Means "any address" or "not yet assigned" depending on context.
255.255.255.255
Broadcast—sent to every host on the local network segment.
IPs in logs are evidence
Firewall logs, web server access logs, and authentication records all capture source IPs. Learning to read and correlate them is a core SOC skill—even before you learn subnetting.
Knowledge Check
How many bits is an IPv4 address?
Multiple choice
Knowledge Check
What is the valid range for each octet in dotted decimal notation?
Multiple choice
Knowledge Check
True or False: 127.0.0.1 is the loopback address used to communicate with the local machine.
True or False