IP Addresses - How Devices Find Each Other
Every connection starts with an address. Here’s how they work.
Every device on a network needs an address. Without one, data has no idea where to go. An IP address is a non-negotiable part of understanding cybersecurity. In 2026, IPs aren’t just on laptops and phones; every IoT device, cloud instance, container, and serverless function has one. A single company might manage tens of thousands of systems across both physical and cloud infrastructure.
IPv4 and IPv6
IPv4 addresses look like 192.168.1., four numbers separated by dots, with values 0–255, for a total of roughly 4.3 billion. We ran out years ago with 20+ billion devices online. IPv6 addresses like 2001:0db8:85a3::8a2e:0370:7334 provide a practically unlimited supply. As of 2026, roughly 45% of global traffic uses IPv6, but IPv4 still dominates day-to-day security work. Dual-stack environments running both can create monitoring blind spots if only one protocol is watched.
Public vs private
Your ISP assigns your public IP address and faces the internet. Your private IP address is used within your local network and is assigned by your router via DHCP. NAT translates between them. The same concept applies in cloud VPCs: private ranges are used internally, with NAT gateways handling public-facing traffic. Memorize the three private ranges: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16.
Static vs dynamic
Static IPs stay constant and are used by servers that need to be reliably found. DHCP assigns dynamic IPs and can change them, which is typical for end-user devices. In incident response, matching a dynamic IP to a specific device at a specific timestamp requires DHCP log correlation.
Why this matters for cybersecurity
Log analysis: Every SIEM alert contains source and destination IPs. Incident response: tracing IPs is step one. Network segmentation: IP ranges separate departments and limit lateral movement. Threat intel: blocklists of malicious IPs cross-referenced against your traffic in real time. Cloud security: ephemeral IPs from containers and auto-scaling require dynamic tracking and rich logging context.
Bottom line
IP addresses are the addressing system of the Internet. Every connection, every attack, every log entry involves them. Understand public vs private, static vs dynamic, IPv4 vs IPv6 - and everything else builds on top. Next up: routers, switches, and firewalls.
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