Bogon Addresses: What Are Invalid IP Ranges?

Learn what bogon addresses are, why they exist, and how internet protocols use these special reserved IP ranges

Updated September 2025 • 8 min read • Security Focus
For Everyone: Whether you're curious about networking or managing IT systems, this guide explains bogon addresses in practical terms

What Are Bogon Addresses?

Bogon addresses are IP addresses reserved for special purposes and not used for regular internet communication. The term "bogon" comes from "bogus" - these are special IP ranges set aside by internet standards for specific functions like private networks, documentation, and testing.

Why Bogon Addresses Exist

Internet protocols reserve these special addresses for important purposes:

  • Private Networks: Your home WiFi and office networks (like 192.168.x.x)
  • System Functions: Computer self-communication (like 127.0.0.1 localhost)
  • Documentation: Examples in technical guides and tutorials
  • Future Use: Space reserved for new internet features

Types of Bogon Addresses

Bogon addresses serve different purposes in internet protocols. Here are the main categories and what they're actually used for:

RFC 1918 Private Addresses
10.0.0.0/8 10.0.0.0 - 10.255.255.255
172.16.0.0/12 172.16.0.0 - 172.31.255.255
192.168.0.0/16 192.168.0.0 - 192.168.255.255

Your home WiFi, office network, and router admin pages use these addresses

Special Use Addresses
0.0.0.0/8 Current network
127.0.0.0/8 Loopback addresses
169.254.0.0/16 Link-local (APIPA)
224.0.0.0/4 Multicast addresses

System functions like localhost, automatic IP assignment, and group communications

Standards References
  • RFC 1918: Private Internet Address Allocation
  • RFC 3927: Dynamic Configuration of IPv4 Link-Local Addresses
  • RFC 5735: Special-Use IPv4 Addresses
  • RFC 6890: Special-Purpose IP Address Registries
  • RFC 3330: Special-Use IPv4 Addresses (obsoleted by 5735)
  • IANA Registry: Special-Purpose Address Registry

Complete Bogon Address List

Here's the comprehensive list of IPv4 bogon addresses that should be filtered at internet boundaries:

Network Range CIDR Description RFC Reference
0.0.0.0 - 0.255.255.255 0.0.0.0/8 "This" network RFC 1122
10.0.0.0 - 10.255.255.255 10.0.0.0/8 Private network Class A RFC 1918
127.0.0.0 - 127.255.255.255 127.0.0.0/8 Loopback addresses RFC 1122
169.254.0.0 - 169.254.255.255 169.254.0.0/16 Link-local addresses RFC 3927
172.16.0.0 - 172.31.255.255 172.16.0.0/12 Private network Class B RFC 1918
192.0.2.0 - 192.0.2.255 192.0.2.0/24 Documentation/example network RFC 5737
192.168.0.0 - 192.168.255.255 192.168.0.0/16 Private network Class C RFC 1918
198.51.100.0 - 198.51.100.255 198.51.100.0/24 Documentation/example network RFC 5737
203.0.113.0 - 203.0.113.255 203.0.113.0/24 Documentation/example network RFC 5737
224.0.0.0 - 239.255.255.255 224.0.0.0/4 Multicast addresses RFC 3171
240.0.0.0 - 255.255.255.255 240.0.0.0/4 Reserved/experimental RFC 1112

How Bogon Addresses Work in Practice

Understanding how these reserved addresses work helps explain why they're important in networking:

Home and Office Networks

Private addresses (192.168.x.x, 10.x.x.x) are used because:

  • Every home can use the same ranges without conflict
  • Routers automatically handle the translation to public IPs
  • It saves millions of public IP addresses
  • Most routers come pre-configured to use these ranges
System Functions

Special addresses serve important purposes:

  • 127.0.0.1: Your computer talking to itself (localhost)
  • 169.254.x.x: Automatic IP when DHCP fails
  • 224.x.x.x: Group communications (like streaming)
  • 0.0.0.0: "Any address" in network configurations
The Reality: Built-In Protection

Modern internet infrastructure automatically handles bogon filtering. Most commercial routers, ISPs, and network equipment have built-in rules that prevent bogon addresses from being routed across the public internet. The average user rarely encounters issues with bogon addresses because this filtering happens automatically.

When You Might Encounter Bogon Addresses

While most users never see bogon issues due to built-in filtering, here are situations where you might encounter them:

Common Scenarios

Home Network Setup

When setting up home networks, you'll work with private addresses:

  • Router admin page: Usually 192.168.1.1 or 10.0.0.1
  • Device IPs: Your laptop might be 192.168.1.100
  • Port forwarding: Using private IPs for game servers
  • Network troubleshooting: Checking local connectivity
Office IT Management

IT professionals work with bogon addresses for:

  • Internal networks: Organizing departments with 10.x.x.x
  • Documentation: Using example IPs in network diagrams
  • Testing: Lab environments with reserved addresses
  • VPN setup: Connecting remote offices securely

Automatic Protection

Why You Don't Need to Worry
  • Router Filtering: Consumer and business routers automatically block bogon routing
  • ISP Protection: Internet service providers filter bogon traffic at network edges
  • Built-in Standards: Network equipment follows RFC standards by default
  • Automatic Updates: Modern systems update bogon lists automatically
  • Protocol Design: Internet protocols are designed to handle these addresses correctly

Dynamic Bogons and Unallocated Space

Beyond static reserved ranges, "dynamic bogons" include currently unallocated IPv4 address space that may be allocated in the future:

The Challenge of IPv4 Exhaustion

As IPv4 addresses become increasingly scarce:

  • IANA Exhaustion: Completed in 2011 - no more /8 blocks to allocate
  • RIR Exhaustion: Regional registries running out of space
  • Dynamic Allocation: Previously bogon space being allocated
  • Filtering Updates: Networks must update bogon lists regularly
Important: Static bogon lists become outdated quickly. Use automated feeds from Team Cymru, IANA, or RIR databases for current unallocated space.

Test Your Network for Bogon Exposure

Use our network analysis tools to check for bogon addresses and validate your filtering effectiveness:

Bogon Detection & Analysis

Our IP analysis platform automatically detects bogon addresses and provides:

  • Real-time Detection: Instant identification of bogon addresses
  • Security Warnings: Alerts for potentially malicious traffic
  • RFC References: Detailed explanations of why addresses are invalid
  • Network Context: Impact analysis for your infrastructure
Check for Bogons

Practical Examples: Using Bogon Addresses

Example: Home Network Setup

Situation: Setting up a home office network

Using Bogon Addresses:

  • Router: 192.168.1.1 (admin interface)
  • Work laptop: 192.168.1.10
  • Home server: 192.168.1.100
  • Smart devices: 192.168.1.20-50

Result: Everything works perfectly! Your router handles all the internet communication.

Example: Testing Web Applications

Situation: Developer testing a web application

Using Bogon Addresses:

  • localhost: 127.0.0.1 (testing on your own computer)
  • Examples: 192.0.2.1 (in documentation)
  • Lab network: 10.0.0.x (isolated test environment)
  • Demo servers: 203.0.113.x (safe example IPs)

Result: Safe testing without affecting real internet traffic.

Conclusion

Bogon addresses are an essential part of how the internet works, providing reserved space for private networks, system functions, and future development. Key takeaways:

  • Essential Function: Bogon addresses serve important purposes in internet protocols
  • Automatic Handling: Modern equipment handles bogon filtering automatically
  • Common Usage: You use bogon addresses every day (home WiFi, localhost)
  • Built-in Protection: Internet infrastructure prevents bogon routing issues
  • Standards-Based: These addresses are defined by international internet standards
Learn More: Explore our complete IP address guide to understand how all IP addresses work together, or use our network analysis tools to see these concepts in action.