IP Ranges and Network Analysis

12 min read•Published Sep 2, 2025

Master CIDR notation, subnetting, and routing concepts. Learn how ranges map to ownership, why ASNs matter, and how to analyze blocks responsibly.

Understanding IP Ranges

Behind every public IP is a larger allocation. Providers hand out addresses in blocks, and networks group them into subnets. Reading those ranges helps you see ownership patterns, data center footprints, and how traffic is routed.

Why ranges matter

  • • ISPs allocate contiguous blocks to customers and services
  • • Security and allowlists operate on ranges, not single hosts
  • • CDN and cloud providers cluster services by blocks
  • • Geolocation and routing are often consistent within a subnet

Example: Google’s public DNS lives inside 8.8.8.0/24. That /24 contains 256 addresses from 8.8.8.0 to 8.8.8.255, including 8.8.8.8 and 8.8.4.4 used by millions every day.

CIDR Notation Explained

CIDR pairs an address with a prefix length, like 192.168.1.0/24. The prefix (/24) says how many leading bits identify the network; the rest are for hosts.

Reading 192.168.1.0/24

192.168.1.0/24
Network

Start of the range

Prefix length

Bits reserved for the network

Common sizes

/8
16,777,216 addresses
Very large allocations
/16
65,536 addresses
Large org or region blocks
/24
256 addresses
Common LAN or service blocks
/32
1 addresses
A single host

Subnet Fundamentals

Subnetting splits a larger network into smaller parts for security, performance, and simpler management.

Example: 10.0.0.0/16 split

10.0.1.0/24Sales
10.0.2.0/24Engineering
10.0.3.0/24Marketing
10.0.4.0/25Servers

Network Calculations

From a CIDR range you can derive network, broadcast, and usable host counts.

192.168.1.0/24 quick math

Network
192.168.1.0

Start of range

Broadcast
192.168.1.255

End of range

First usable
192.168.1.1

Assign to hosts

Last usable
192.168.1.254

Assign to hosts

Total
256

All addresses

Usable
254

Excludes network/broadcast

• Total IPs = 2^(32 - prefix)
• Usable IPs ≈ Total − 2 (IPv4, traditional)
• Subnet mask: prefix bits set to 1, rest 0

IP Block Allocation

The address space flows from IANA to RIRs to ISPs and organizations, then to end users.

1
IANA

Global policy, hands /8-scale blocks to RIRs

2
RIRs

Regional registries (ARIN, RIPE, APNIC, AFRINIC, LACNIC)

3
ISPs & Orgs

Receive blocks and sub-allocate to customers and services

4
End users

Use assigned IPs for devices and servers

Autonomous Systems (AS)

An AS groups networks under one routing policy. ASNs (e.g., AS15169) help tie ranges to owners and paths.

Familiar ASNs

AS15169
Google LLC
AS16509
Amazon.com, Inc.
AS13335
Cloudflare, Inc.
  • Ownership: Who operates the network
  • Paths: How BGP forwards traffic across providers
  • Scope: Regional vs global footprints
  • Service type: ISP, cloud, hosting, CDN

Network Routing Concepts

How routers use ranges

Aggregation

Routers keep routes for blocks instead of every IP.

8.8.8.0/24 → Google
Longest‑prefix match

When many routes match, the most specific wins.

8.8.8.8 matches /8 and /24 → choose /24

Network Analysis Techniques

Practical ways to study ranges and ownership:

WHOIS lookups

Read registration for blocks

Tools: whois, web WHOIS
Use case: Find owners and contacts

BGP routes

Inspect paths and peers

Tools: looking glasses, RouteViews, RIPE
Use case: Understand AS relationships

Range scans

Probe blocks to map active hosts

Tools: Nmap, Masscan, Zmap
Use case: Discovery and audits

Geo correlation

Compare locations across blocks

Tools: various GeoIP tools
Use case: Spot data centers and coverage

Use this responsibly

Get permission before scanning, follow terms, and practice responsible disclosure.

Key Takeaways

Remember these points:

  • CIDR expresses ranges with a prefix length (e.g., /24)
  • Subnets improve security, performance, and management
  • ASNs link ranges to real network owners and routing policies
  • Routers choose the most specific route (longest prefix)
  • Ethical analysis starts with permission and clear scope

Table of Contents