What is the IP address 100.64 0.0 10?

Published On - March 3, 2025

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The IP address 100.64.0.0/10 is a special range of IP addresses assigned by the Internet Assigned Numbers Authority (IANA) for carrier-grade NAT (CGNAT). This range, defined in RFC 6598, is intended for use by Internet service providers (ISPs) to manage networks where multiple customers share a limited number of public IPv4 addresses.

What is the 100.64.0.0/10 Address Block?

The 100.64.0.0/10 address block covers IPs from 100.64.0.0 to 100.127.255.255. It includes 4,194,304 addresses, making it a large reserved space for service providers to implement carrier-grade NAT. This practice allows ISPs to extend the life of IPv4 by enabling multiple users to share a single public IP address.

Purpose of 100.64.0.0/10

This IP range was introduced to solve the issue of IPv4 exhaustion. Instead of providing every customer with a unique public IPv4 address, ISPs assign them private IPs within the 100.64.0.0/10 range and use Network Address Translation (NAT) at a large scale to forward traffic through shared public IPv4 addresses.

Key Uses of the 100.64.0.0/10 Range:

  • Carrier-Grade NAT (CGNAT): ISPs use it to assign internal addresses to customers.
  • Private Networking: Some organizations use it for internal communication where traditional private IP ranges (RFC 1918) are insufficient.
  • IPv4 Conservation: Helps delay the transition to IPv6 by reusing IPv4 addresses.

How 100.64.0.0/10 Differs from Private IPv4 Addresses

Unlike the traditional private IP ranges (10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16), 100.64.0.0/10 is specifically designed for ISPs rather than individual end-users. It is meant to be an internal service provider network rather than a home or business LAN.

Issues and Limitations

Using CGNAT with 100.64.0.0/10 has its downsides, including:

  • Port Restrictions: Multiple users sharing a single public IP can lead to limited availability of ports, affecting applications that need open ports, such as gaming and VoIP.
  • Traceability Challenges: ISPs must maintain logs to track user activity since multiple users share public IPs.
  • Incompatibility with Some Services: Certain online services do not function properly with CGNAT due to difficulties in identifying individual users.

Alternative Solutions

The ideal long-term solution to IPv4 exhaustion is the adoption of IPv6. Unlike IPv4, IPv6 provides a vastly larger address space, eliminating the need for NAT altogether. Many ISPs and organizations are gradually shifting to IPv6, although IPv4 is still dominant.

Check Your Internet Connection

Frequently Asked Questions (FAQ)

Is 100.64.0.0/10 a private IP range?

It is not a traditional private range like those defined in RFC 1918. Instead, it is considered a shared address space specifically for ISPs implementing CGNAT.

Can I use 100.64.0.0/10 for my home network?

It is not recommended. Home and business networks should use private IP ranges such as 10.0.0.0/8 or 192.168.0.0/16 instead.

Why can’t I host a server if my IP starts with 100.64?

Since this range is used in CGNAT, your IP is not publicly accessible. This prevents direct inbound connections, making it difficult to host services without additional configurations.

Does 100.64.0.0/10 affect my internet speed?

Not directly, but CGNAT can introduce minor latency due to the processing required for NAT translation. However, the impact is usually small.

How do I check if my ISP is using CGNAT?

Check your assigned IP on your router and compare it with your public IP (visible through sites like whatismyip.com). If they are different and your private IP is within 100.64.0.0/10, your ISP is using CGNAT.

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