Private & Reserved IP Address Reference

Enter any IPv4 address to identify which reserved or special-purpose range it belongs to. This tool checks against all RFC 1918 private ranges, loopback, link-local, multicast, CGNAT, documentation, and other IANA-reserved blocks. Browse the complete reference table below for all reserved IPv4 ranges.

Understanding Private and Reserved IP Addresses

Not all IP addresses are created equal. The Internet Assigned Numbers Authority (IANA) has designated specific ranges for private networks, testing, documentation, multicast, and other special purposes. These addresses are never routed on the public internet — they exist only within local networks or specific protocol contexts.

The most commonly used reserved ranges are the RFC 1918 private addresses: 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. Every home and business network uses these ranges internally, with NAT (Network Address Translation) translating them to a public IP for internet access. If you've ever logged into your router at 192.168.1.1 or 10.0.0.1, you've used private IP addresses.

Complete RFC 1918 Private Address Ranges

RFC 1918 defines three private address blocks that organizations can use freely without registration. These ranges are the foundation of virtually every local network:

To plan how to divide these ranges into subnets for your network, use our IP Address Planner. For calculating specific subnets, the Subnet Calculator can determine network addresses, broadcast addresses, and usable host ranges.

Pro Tip: When choosing a private range, consider potential VPN conflicts. If your office uses 192.168.1.0/24 and your home network also uses 192.168.1.0/24, connecting via VPN creates routing conflicts. Use less common subnets (like 10.47.0.0/16 or 172.22.0.0/16) for corporate networks to minimize VPN overlap. Check our IP Range Calculator to verify your planned ranges don't overlap.

All Reserved and Special-Purpose IPv4 Ranges

Beyond RFC 1918, IANA has reserved many other ranges for specific purposes. Understanding these helps when troubleshooting unexpected addresses in network logs or configuring firewalls:

Carrier-Grade NAT (CGNAT) - RFC 6598

The 100.64.0.0/10 range is a relatively new reserved block (2012) designed for ISP use. As IPv4 addresses became scarce, ISPs began using Carrier-Grade NAT to share a single public IP among multiple subscribers. The CGNAT range sits between your private network and the public internet — your traffic goes through two layers of NAT.

You might encounter CGNAT addresses when you check your router's WAN IP. If your router at 192.168.1.1 shows a WAN IP in the 100.64-100.127 range, you're behind CGNAT. This can affect port forwarding, online gaming, and hosting services. Compare your WAN IP with our What Is My IP tool — if they differ, you're likely behind CGNAT.

Link-Local Addresses (169.254.x.x)

Link-local addresses (169.254.0.0/16) are automatically assigned by a host when it cannot obtain an address from a DHCP server. This is called APIPA (Automatic Private IP Addressing) on Windows. If you see a 169.254.x.x address on your device, it indicates a DHCP problem.

# Check for link-local addresses on Windows
ipconfig | findstr "169.254"

# Check on Linux/macOS
ip addr show | grep "169.254"

# Common fixes:
# 1. Restart the DHCP client
#    Windows: ipconfig /release && ipconfig /renew
#    Linux: sudo dhclient -r && sudo dhclient
# 2. Check router DHCP server is enabled
# 3. Verify network cable/WiFi connection
# 4. Restart router (at 192.168.1.1 or 10.0.0.1)

If your devices are consistently getting link-local addresses, the issue is usually a misconfigured or disabled DHCP server on your router. Log in to your router's admin panel and verify DHCP is enabled. See our troubleshooting guide for related connectivity issues.

Documentation Ranges (TEST-NET)

Three /24 blocks are reserved specifically for use in documentation, examples, and educational materials. If you see these addresses in tutorials, textbooks, or configuration examples, they are intentionally non-routable:

• 192.0.2.0/24 (TEST-NET-1) — From RFC 5737, commonly used in IETF documents.
• 198.51.100.0/24 (TEST-NET-2) — Used in examples and documentation.
• 203.0.113.0/24 (TEST-NET-3) — Used in examples and documentation.

These are the IPv4 equivalent of "example.com" for domain names. Using them in documentation avoids accidentally referencing real IP addresses that could belong to actual organizations. Network engineers should use these ranges in all documentation, training materials, and DNS configuration examples.

Identifying Public vs Private Addresses

When troubleshooting network issues, quickly identifying whether an address is public or private is essential. The classifier tool above automates this, but understanding the logic helps:

# Quick reference for identifying private IPs:
# 10.x.x.x      → Private (RFC 1918)
# 172.16-31.x.x  → Private (RFC 1918)
# 192.168.x.x    → Private (RFC 1918)
# 100.64-127.x.x → CGNAT (RFC 6598)
# 127.x.x.x      → Loopback
# 169.254.x.x    → Link-Local (APIPA)
# 224-239.x.x.x  → Multicast
# 240-255.x.x.x  → Reserved/Broadcast
# Everything else → Public (probably)

For a deeper analysis, use our Network Class Identifier to determine the classful designation, or the IP Lookup tool to find ISP and geolocation data for public addresses. Understanding the difference is critical when configuring NAT rules on your gateway.

Video: Private vs Public IP Addresses

Related Guides

• Subnet Calculator
• IP Address Planner
• IP Range Calculator
• CIDR Converter
• Network Class Identifier
• Multicast IP Reference
• IP Address Lookup
• What Is an IP Address?
• What Is NAT?
• What Is a Subnet Mask?
• Default Router IP Addresses

Frequently Asked Questions

What are RFC 1918 addresses?

RFC 1918 defines three IPv4 address ranges reserved for private networks: 10.0.0.0/8 (16.7M addresses), 172.16.0.0/12 (1M addresses), and 192.168.0.0/16 (65K addresses). These addresses are not routed on the public internet and can be used freely by any organization. Your home router uses these for your local network, with NAT providing internet access.

Is 192.168.1.1 a private IP address?

Yes, 192.168.1.1 falls within the 192.168.0.0/16 private range defined by RFC 1918. It is the most common default gateway address for home routers. You can access your router's admin panel by navigating to 192.168.1.1 in your browser.

What is CGNAT and how do I know if I'm behind it?

CGNAT (Carrier-Grade NAT) is when your ISP uses the 100.64.0.0/10 range to share a single public IP among multiple subscribers. Check your router's WAN IP — if it starts with 100.64-100.127, you're behind CGNAT. Compare it with your public IP from our What Is My IP tool; if they differ, CGNAT is in use.

Why is my device getting a 169.254.x.x address?

A 169.254.x.x address (APIPA/link-local) means your device failed to obtain an IP from a DHCP server. Common causes include: DHCP server disabled on the router, network cable unplugged, WiFi disconnected, or the DHCP pool is exhausted. Check your router's DHCP settings at 192.168.1.1.

Can two devices on different networks have the same private IP?

Yes, private IP addresses are only unique within a single network. Millions of home networks worldwide use 192.168.1.1 as their gateway simultaneously. NAT ensures each network appears as a different public IP on the internet. This address reuse is exactly why private ranges were created — to conserve the limited IPv4 public address space.

What is the difference between 10.x.x.x and 192.168.x.x?

Both are private address ranges, but they differ in size. 10.0.0.0/8 provides 16.7 million addresses (suitable for large organizations), while 192.168.0.0/16 provides 65,536 addresses (suitable for home and small business). Functionally, there is no performance or security difference — the choice depends on how many addresses you need. Use our IP Address Planner to design your allocation.

Are multicast addresses considered private?

Multicast addresses (224.0.0.0/4) are neither private nor public in the traditional sense. They are destination-only addresses used for one-to-many communication. They are reserved by IANA and not assigned to individual hosts. The administratively scoped range (239.0.0.0/8) functions similarly to private addresses, staying within an organization. See our Multicast IP Reference for the complete list.

About Tommy N.

Tommy is the founder of RouterHax and a network engineer with 10+ years of experience in home and enterprise networking. He specializes in router configuration, WiFi optimization, and network security. When not writing guides, he's testing the latest mesh WiFi systems and helping readers troubleshoot their home networks.