CGNAT (Carrier-Grade Network Address Translation), also called Carrier-Grade NAT (CGN) or Large-Scale NAT (LSN), is a networking technology used by Internet Service Providers (ISPs) to allow multiple customers to share one or a smaller pool of public IPv4 addresses.

Traditional NAT normally happens inside your home or office router. Your computers, phones, printers, CCTV cameras, and other devices use private IP addresses such as:

• 192.168.1.10
• 192.168.1.20
• 10.0.0.15

Your router translates these private addresses into the public IPv4 address assigned by your ISP.

With CGNAT, there is another NAT system inside the ISP's network.

Therefore, your connection may effectively look like:

Computer → Local Router NAT → ISP CGNAT → Public IPv4 → Internet

RFC 6888 defines a Carrier-Grade NAT as a NAT function operated by the service provider that allows the same IPv4 address to be shared among multiple subscribers. Unlike your own router's NAT, the ISP's CGNAT is generally outside your control.

Why Do ISPs Use CGNAT?

The primary reason is IPv4 address exhaustion.

IPv4 uses 32-bit addresses, providing roughly 4.3 billion possible addresses. The growth of computers, smartphones, broadband connections, servers, IoT devices, and other Internet-connected equipment created far more demand than the original IPv4 system could comfortably accommodate.

Instead of assigning a unique public IPv4 address to every customer, an ISP can place hundreds or potentially thousands of subscriber connections behind shared public IPv4 addresses.

CGNAT therefore allows ISPs to conserve their limited IPv4 address inventory while the Internet continues transitioning toward IPv6.

Normal NAT vs CGNAT

Understanding the difference is important.

Traditional NAT

A normal home network might look like:

PC: 192.168.1.10
        ↓
Router
        ↓
Public IP: 203.x.x.x
        ↓
Internet

The public IPv4 address belongs to your Internet connection.

You normally control the router performing NAT.

CGNAT

With CGNAT:

PC
192.168.1.10
      ↓
Home Router
      ↓
ISP-side / Shared Address
100.72.x.x
      ↓
ISP CGNAT Gateway
      ↓
Shared Public IPv4
203.x.x.x
      ↓
Internet

The ISP performs another translation before your traffic reaches the public Internet.

This architecture is sometimes described as NAT444, because traffic passes through the customer's private IPv4 network, the provider's addressing/NAT environment, and the public IPv4 Internet.

What Is the CGNAT IP Range?

RFC 6598 reserved the following IPv4 network specifically as Shared Address Space for service-provider CGN deployments:

100.64.0.0/10

This covers:

100.64.0.0
to
100.127.255.255

This address space is not normal globally routable public IPv4 space and is distinct from the familiar RFC 1918 private address ranges.

Common RFC 1918 private ranges include:

10.0.0.0/8

172.16.0.0/12

192.168.0.0/16

CGNAT shared space is:

100.64.0.0/10

So if your router's WAN address is something such as:

100.64.x.x
100.72.x.x
100.100.x.x
100.120.x.x

CGNAT is a strong possibility.

Important: 100.x.x.x Does Not Always Mean CGNAT

Do not assume that every address beginning with 100 is CGNAT.

Only:

100.64.0.0 – 100.127.255.255

belongs to the RFC 6598 Shared Address Space.

For example:

100.50.x.x

is outside the CGNAT block.

Similarly:

100.200.x.x

is outside the CGNAT block.

How CGNAT Works

Suppose three ISP customers are connected:

Customer A
Customer B
Customer C

Instead of providing each customer with a dedicated public IPv4 address, the ISP may assign internal/shared addresses:

Customer A → 100.64.10.1
Customer B → 100.64.10.2
Customer C → 100.64.10.3

The ISP's CGNAT gateway may then translate all these connections through:

203.0.113.x

or another public address from its public IPv4 pool.

The NAT gateway keeps track not only of IP addresses but also TCP/UDP ports and connection state so that response traffic can be returned to the correct subscriber.

Conceptually:

Customer A:10001 ─┐
Customer B:20001 ─┼──> Shared Public IPv4
Customer C:30001 ─┘

The real implementation can be considerably more complex, but this illustrates why many subscribers can appear to Internet servers as the same public IP address.

How to Check Whether Your Internet Uses CGNAT

One of the simplest methods is to compare your router's WAN/Internet IP address with the public IPv4 address visible on the Internet.

Step 1 – Find the Router WAN IP

Log in to your broadband router.

Common addresses include:

192.168.0.1
192.168.1.1
192.168.100.1

Look under sections such as:

Internet
WAN
Internet Status
Network Status
IPv4 WAN
Connection Information

Suppose the router shows:

WAN IP: 100.72.18.24

Step 2 – Check Your Public IPv4 Address

Use a public IP-checking service or search for:

what is my IP

Suppose the Internet reports:

49.x.x.x

Now you have:

Router WAN IP:     100.72.18.24
Internet Public IP: 49.x.x.x

These addresses are different, and the WAN address is inside 100.64.0.0/10.

That is strong evidence that your connection is behind CGNAT.

Can a Different WAN and Public IP Always Prove CGNAT?

Not necessarily.

A mismatch indicates that another translation layer exists upstream, but the provider might use another private/internal addressing design rather than RFC 6598 shared space.

For example, your router might receive:

10.x.x.x
172.16.x.x – 172.31.x.x
192.168.x.x

from the provider.

You may still be behind provider-side NAT even though the address is not in 100.64.0.0/10.

Therefore, the most reliable approach is to combine:

1. WAN IP inspection
2. Public IP comparison
3. Traceroute testing
4. Port-forwarding tests
5. Confirmation from the ISP

Checking CGNAT with Traceroute

Windows users can run:

tracert 8.8.8.8

Linux and macOS users can use:

traceroute 8.8.8.8

If several private or shared-address hops appear before public Internet hops, provider-side NAT may be present.

Traceroute alone, however, should not be treated as absolute proof because routers may suppress, alter, or differently handle traceroute responses.

Why Port Forwarding Often Does Not Work Behind CGNAT

This is one of the biggest practical disadvantages.

Suppose you configure:

TCP Port 3389

for Windows Remote Desktop.

Your router may correctly forward:

Public/WAN Port 3389
        ↓
192.168.1.20:3389

But incoming Internet traffic first reaches the ISP's public address and its CGNAT gateway.

You normally cannot configure the ISP's NAT gateway.

Therefore:

Internet
   ↓
ISP Public IP
   ↓
CGNAT   ← Connection cannot automatically reach your router
   ↓
Your Router
   ↓
Your PC

This is why conventional inbound port forwarding frequently fails behind CGNAT.

Does DMZ Solve CGNAT?

Usually no.

Placing a device in your router's DMZ only changes how your own router handles incoming connections.

It does not remove the upstream ISP NAT.

For example:

Internet
   ↓
ISP CGNAT
   ↓
Your Router DMZ
   ↓
Server

Traffic still has to cross the ISP's CGNAT first.

Does UPnP Solve CGNAT?

Usually no.

UPnP can automatically create port mappings on your local router, but it normally cannot control the ISP's CGNAT gateway.

Therefore, UPnP may work perfectly on your router while inbound Internet connections still fail.

Does DDNS Solve CGNAT?

This is another common misunderstanding.

Dynamic DNS services provide a hostname such as:

myoffice.example.com

that points toward an Internet-facing IP address.

But DDNS does not automatically create an inbound path through CGNAT.

Therefore:

DDNS + CGNAT

usually does not solve traditional inbound port-forwarding requirements.

DDNS solves the problem of a changing public address, while CGNAT creates an inbound reachability/NAT problem.

They are different issues.

Common Applications Affected by CGNAT

CGNAT can affect applications that require unsolicited inbound connections or direct peer-to-peer connectivity.

Examples include:

Remote Desktop

Direct RDP access using:

Public-IP:3389

may not work.

CCTV / DVR / NVR

Traditional CCTV systems that depend on router port forwarding may become inaccessible remotely.

Modern cloud/P2P-based CCTV systems may still work because they typically establish outbound connections.

Home Servers

Hosting:

Web server
FTP server
Game server
Mail server
NAS
Media server

may be difficult without an alternative connectivity method.

Online Gaming

Some games and consoles may report:

Strict NAT
Moderate NAT
NAT Type 3

depending on their NAT classification system.

Peer-to-peer matchmaking, hosting games, and voice communication can sometimes be affected.

Peer-to-Peer Applications

Some P2P applications may have reduced inbound connectivity.

VPN Servers

Running your own:

WireGuard server
OpenVPN server
IPsec VPN server

behind CGNAT can be problematic if Internet clients need to initiate connections directly toward your network.

Can a VPN Work Behind CGNAT?

Yes, but an important distinction must be made.

VPN Client

If your computer connects outward to a commercial or corporate VPN server:

Your PC → VPN Server

CGNAT usually does not prevent this.

VPN Server

If you want Internet users to connect:

Internet → Your VPN Server

CGNAT becomes a problem because inbound connections must reach your server.

Overlay VPN and NAT-traversal technologies can provide alternatives.

CGNAT and Remote Desktop

A traditional remote-access configuration might be:

Internet
   ↓
Static Public IP
   ↓
Router Port Forward
   ↓
RDP Computer

CGNAT changes this to:

Internet
   ↓
ISP CGNAT
   ↓
Customer Router
   ↓
RDP Computer

Therefore, configuring port forwarding only on the customer router is insufficient.

For business RDP environments, a public static IP, properly configured VPN, RD Gateway, or secure overlay network is generally preferable to exposing RDP directly to the Internet.

Security Warning About RDP

Even when you obtain a public IPv4 address, directly exposing TCP 3389 to the Internet is generally not recommended.

A safer architecture is:

Internet
   ↓
VPN / Secure Gateway
   ↓
Internal Network
   ↓
RDP Server

Use strong authentication, account lockout policies, MFA where supported, firewall restrictions, regular patching, and appropriate monitoring.

Solutions for CGNAT

If CGNAT prevents an application from working, several solutions are available.

1. Ask the ISP for a Public IPv4 Address

Contact the ISP and ask:

Can you remove CGNAT from my connection and provide a public IPv4 address?

Some providers offer this free, while others charge an additional fee.

2. Purchase a Static Public IPv4 Address

For business connections, this is often the cleanest solution.

You receive an address such as:

Public Static IPv4
        ↓
Your Router
        ↓
Firewall
        ↓
LAN

You can then configure controlled inbound services.

A static public IP is useful for:

• Site-to-site VPN
• Office VPN server
• CCTV
• Remote-access gateways
• Hosting
• Business firewall rules
• Certain server applications

3. Use IPv6

IPv6 was designed partly to solve the address-scarcity problem that made technologies such as CGNAT necessary.

If both your ISP and application support IPv6, devices can have globally routable IPv6 addresses without relying on IPv4 CGNAT for IPv6 traffic.

However, globally routable does not mean unrestricted.

A firewall should still control inbound IPv6 connections.

4. Use an Overlay VPN

Overlay networking technologies can establish outbound connections and use NAT traversal to connect devices without conventional port forwarding.

This approach can be useful for:

Remote desktop
NAS access
Server administration
Private application access
Office-to-office connectivity

Depending on the service and network conditions, traffic may connect peer-to-peer or use a relay.

5. Use a Reverse Tunnel

Instead of the Internet initiating a connection toward your CGNAT connection:

Internet → Your Server

your internal server establishes an outbound connection:

Your Server → Internet Relay/VPS

Remote clients then connect through the externally reachable system.

This reverses the normal connection direction and can work even when traditional inbound port forwarding is unavailable.

6. Use a VPS

Another architecture is:

Office Server
     ↓
Encrypted Tunnel
     ↓
VPS with Public IP
     ↑
Remote User

The VPS provides the publicly reachable endpoint.

Traffic is then transported securely to the private network.

CGNAT vs Double NAT

They are related but not identical.

Double NAT means traffic passes through two NAT devices.

For example:

PC
 ↓
Wi-Fi Router
 ↓
ISP Modem/Router
 ↓
Internet

Both devices might actually belong to you or be installed at your premises.

CGNAT means one NAT layer exists inside the service provider's network and is not normally controlled by the subscriber.

You can even have:

Local Double NAT
+
ISP CGNAT

creating several translation layers.

CGNAT vs NAT444

NAT444 describes an architecture involving three IPv4 addressing domains:

Customer Private IPv4
        ↓
Provider/Shared IPv4
        ↓
Public IPv4 Internet

CGNAT is commonly used as part of such an architecture.

CGNAT vs Static Public IP

Feature	CGNAT	Static Public IPv4
Unique public IPv4	Usually No	Yes
Shared with other customers	Usually Yes	No
Direct inbound connectivity	Restricted	Possible
Traditional port forwarding	Usually problematic	Supported
CCTV hosting	Can be difficult	Easier
Direct VPN server	Can be difficult	Supported
Self-hosting	Difficult	Easier
IP remains unchanged	Not guaranteed	Yes
Additional ISP charge	Often included	Often charged

CGNAT vs Dynamic Public IP

A dynamic public IP can still be a real public IPv4 address.

For example:

Today: 49.x.x.10
Tomorrow: 49.x.x.75

Even though the address changes, it may still allow port forwarding.

You can often combine:

Dynamic Public IP + DDNS

for remote connectivity.

CGNAT is different because the Internet-facing IPv4 address is shared or translated upstream by the provider.

Does CGNAT Make the Internet Slower?

Not necessarily.

For normal activities such as:

Web browsing
YouTube
Email
Cloud applications
Streaming
Software downloads
Social media

many users will never notice CGNAT.

However, CGNAT introduces another stateful translation system into the path.

Performance can potentially be affected by:

• ISP CGN capacity
• Port allocation
• Session limits
• NAT table load
• Implementation quality
• Network congestion
• Routing
• Application NAT behavior

CGN requirements exist precisely because address sharing can affect application behavior, and some applications may require adaptations or may not function correctly in certain CGN environments.

Does CGNAT Increase Ping?

CGNAT itself does not automatically mean high latency.

The additional processing can add overhead, but in a well-designed provider network it may be small.

High ping is more commonly influenced by:

Distance
ISP routing
Network congestion
Wi-Fi quality
Peering
Server location
Packet loss
Mobile network conditions

Therefore, finding CGNAT does not automatically explain a high-ping problem.

CGNAT and IP-Based Blocking

Another potential problem arises because multiple unrelated subscribers can appear on the Internet using the same public IPv4 address.

Suppose:

Customer A
Customer B
Customer C
Customer D

all appear as:

Public IP X

If one subscriber generates abusive or suspicious traffic, a website that blocks only the shared IP could potentially affect other subscribers as collateral damage.

Large-scale address sharing can therefore complicate IP reputation, rate limiting, security enforcement, and user attribution.

CGNAT and Security Logs

When many subscribers share the same public IPv4 address, the public address alone may not uniquely identify the originating subscriber at a specific moment.

Additional information such as:

Timestamp
Public IPv4
Source port
Protocol

can become important.

IPv6 operational security guidance also notes that large-scale address sharing can complicate attribution and discusses logging source TCP/UDP ports as part of identifying users behind CGN.

Is CGNAT More Secure?

CGNAT can make unsolicited inbound connections more difficult, but it should not be considered a replacement for a firewall.

Security should still include:

Firewall
Endpoint protection
Patch management
Strong passwords
MFA
Network segmentation
Secure remote access
Monitoring
Backups

NAT and security are different concepts.

CGNAT on Mobile Networks

CGNAT is especially common on:

4G
LTE
5G
Mobile broadband
Wireless ISP connections

Mobile operators have extremely large numbers of devices and limited IPv4 address resources, making large-scale address sharing useful.

This is one reason running inbound servers directly over mobile Internet connections can be difficult.

CGNAT on Fiber Broadband

Fiber does not guarantee a public IPv4 address.

You can have:

1 Gbps Fiber
+
CGNAT

Connection technology and IP allocation policy are separate matters.

Therefore, even a very fast fiber connection may require a public-IP add-on for traditional inbound connectivity.

Why Does My Router Show 100.64.x.x?

If your WAN interface shows something like:

100.64.x.x
100.70.x.x
100.100.x.x
100.120.x.x

the ISP is likely using the RFC 6598 Shared Address Space.

RFC 6598 specifically allocated 100.64.0.0/10 for this purpose.

Does Restarting the Router Remove CGNAT?

Usually no.

Restarting may change the shared address assigned to your connection or the public address through which traffic exits.

But CGNAT is an ISP network architecture.

Only the ISP can normally move your connection from:

CGNAT

to:

Public IPv4

unless you use another technical workaround such as an overlay network or externally hosted tunnel.

Can You Disable CGNAT from Your Router?

Normally no.

The CGN device belongs to the ISP.

Settings such as:

Bridge mode
DMZ
UPnP
Port forwarding
Router firewall

do not normally disable provider-side CGNAT.

Contact the ISP if you require a public IPv4 address.

Practical CGNAT Troubleshooting Checklist

When remote connectivity is not working, check in this order:

Step 1

Find your router WAN IPv4 address.

Step 2

Find the IPv4 address visible from the Internet.

Step 3

Compare the two.

Step 4

Check whether the WAN address falls inside:

100.64.0.0 – 100.127.255.255

Step 5

Also check whether your WAN address is an RFC 1918 private address.

Step 6

Run:

tracert 8.8.8.8

on Windows if additional network-path information is required.

Step 7

Ask your ISP:

Is my broadband connection behind CGNAT?

Step 8

If yes, ask:

Can you provide a public dynamic IPv4 address?

or:

Can you provide a static public IPv4 address?

Step 9

If public IPv4 is unavailable, consider:

IPv6
Overlay VPN
Reverse tunnel
VPS
Cloud-based remote-access solution

Example Diagnosis

Suppose a customer reports:

I configured port forwarding for my CCTV DVR, but it doesn't work outside my office.

Router information:

LAN IP: 192.168.1.1
DVR: 192.168.1.50
WAN IP: 100.78.25.10

Public IP checker:

49.x.x.x

Analysis:

100.78.25.10

falls inside:

100.64.0.0/10

and differs from the Internet-visible IPv4 address.

CGNAT is therefore the likely reason ordinary router port forwarding cannot expose the DVR directly.

Possible solutions include obtaining a public IPv4 address from the ISP or using an appropriate secure remote-access/cloud solution.

Advantages of CGNAT

CGNAT provides important benefits to ISPs.

Conserves IPv4 Addresses

Many customers can share limited public IPv4 resources.

Allows Continued IPv4 Service

Providers can continue adding subscribers despite IPv4 scarcity.

Transparent for Common Internet Usage

Most normal outbound applications work without requiring users to understand CGNAT.

Reduces Immediate Dependence on Additional IPv4 Inventory

This is financially and operationally important because public IPv4 addresses are scarce resources.

Disadvantages of CGNAT

The disadvantages become significant for advanced users and businesses.

Port Forwarding Problems

Traditional inbound forwarding usually cannot cross the provider's NAT without provider support.

Self-Hosting Becomes Difficult

Hosting servers directly from the connection is more complicated.

Gaming Issues

Some peer-to-peer gaming scenarios may experience NAT restrictions.

Remote CCTV Issues

Older DVR/NVR solutions dependent on direct inbound connections may fail.

VPN Server Problems

Hosting your own VPN endpoint can become difficult.

Shared IP Reputation

Actions of unrelated subscribers can sometimes affect reputation or rate limits associated with a shared public IP.

Troubleshooting Complexity

Users may configure their routers correctly yet still fail connectivity tests because another NAT exists inside the ISP.

Attribution Complexity

A public IPv4 address may correspond to multiple subscribers, requiring more detailed logging to identify individual connections.

When Should You Request a Public Static IP?

A public static IPv4 address may be worth considering when you operate:

• Business VPN
• Site-to-site VPN
• CCTV/NVR
• Remote-access gateway
• On-premises server
• Hosted business application
• Firewall requiring IP allowlisting
• Services requiring predictable inbound connectivity

For ordinary web browsing, streaming, email, and cloud applications, CGNAT may cause no noticeable problem.

CGNAT FAQ

1. What does CGNAT mean?

CGNAT means Carrier-Grade Network Address Translation. It allows an ISP to share public IPv4 addresses among multiple subscribers.

2. Why does my ISP use CGNAT?

Primarily because public IPv4 addresses are scarce.

3. What is the CGNAT IP range?

The RFC 6598 Shared Address Space is:

100.64.0.0/10

covering 100.64.0.0 through 100.127.255.255.

4. Is 100.64.x.x a public IP?

Addresses within 100.64.0.0/10 are special Shared Address Space intended for service-provider CGN use and are not globally routable public IPv4 addresses.

5. Is 192.168.x.x CGNAT?

No. 192.168.0.0/16 is RFC 1918 private address space. However, if your ISP gives your WAN interface such an address, you may still be behind an upstream NAT.

6. How do I know whether I am behind CGNAT?

Compare your router's WAN IPv4 address with the public IPv4 address visible on the Internet. A different address combined with a WAN address in 100.64.0.0/10 strongly indicates CGNAT.

7. Why doesn't port forwarding work with CGNAT?

Because your router is not the only NAT device. The ISP also performs NAT upstream, and you generally cannot configure the ISP's NAT mapping.

8. Will DMZ fix CGNAT?

Normally no. DMZ changes your router's forwarding behavior but does not remove ISP-side NAT.

9. Will UPnP bypass CGNAT?

Normally no. UPnP typically controls your local router, not the provider's CGN gateway.

10. Does DDNS bypass CGNAT?

No. DDNS maps a hostname to an address; it does not automatically create an inbound path through CGNAT.

11. Can I use RDP behind CGNAT?

Yes, but traditional direct port forwarding may fail. Use a public IP with a secure VPN/gateway, or an appropriate overlay remote-access solution.

12. Can CCTV work behind CGNAT?

Yes. Cloud/P2P-based systems frequently work because they initiate outbound connectivity. Traditional direct-IP CCTV access may require a public IP or alternative tunnel.

13. Can I run a VPN client behind CGNAT?

Usually yes because the client initiates the outbound connection.

14. Can I host a VPN server behind CGNAT?

It is more difficult because external clients cannot normally initiate a connection directly through the ISP's CGNAT.

15. Does CGNAT affect gaming?

It can. Some games and consoles depend on inbound or peer-to-peer connectivity and may report restrictive NAT types.

16. Does CGNAT affect Internet speed?

Not necessarily. Properly implemented CGNAT can handle normal Internet traffic without a noticeable reduction in speed.

17. Does CGNAT increase latency?

It can add processing, but CGNAT alone does not necessarily cause significant latency. Routing, congestion, Wi-Fi, distance, and peering are often more important.

18. Is CGNAT secure?

It can reduce direct unsolicited inbound reachability, but it is not a substitute for a firewall or other security controls.

19. Can I disable CGNAT myself?

Usually no. CGNAT is controlled by the ISP.

20. Can my ISP remove CGNAT?

Possibly. Ask whether they offer a public dynamic IPv4 or static IPv4 service.

21. Is static IP the best CGNAT solution?

For many business applications requiring reliable inbound IPv4 connectivity, a static public IPv4 address is the simplest solution.

22. Can IPv6 solve CGNAT problems?

For applications and networks that support IPv6 end-to-end, IPv6 can avoid the need for IPv4 CGNAT. Proper IPv6 firewall configuration is still essential.

23. Is CGNAT the same as double NAT?

No. Double NAT simply means two NAT layers. CGNAT specifically refers to provider-operated large-scale NAT.

24. What is NAT444?

NAT444 describes an IPv4 architecture involving customer private addressing, provider/shared addressing, and public IPv4 addressing.

25. Why does my WAN IP differ from my public IP?

An upstream NAT, including CGNAT, is one possible explanation.

26. Can Tailscale-style networking work behind CGNAT?

Overlay networking technologies are specifically useful in NAT environments because they can use outbound connectivity and NAT traversal, with relays available when direct peer-to-peer connectivity cannot be established.

27. Can a reverse tunnel bypass CGNAT?

Yes. An internal system can establish an outbound connection to an Internet-reachable server, avoiding the need for a conventional inbound port-forwarding rule.

28. Can a VPS help?

Yes. A VPS with a public IP can act as the Internet-facing endpoint, with an encrypted tunnel connecting it to your CGNAT network.

29. Is CGNAT common on 4G and 5G?

Yes. Large mobile networks are a common environment for address sharing because they serve very large numbers of devices.

30. Is CGNAT going away?

As IPv6 adoption grows, dependence on IPv4 CGNAT should decrease. However, IPv4 remains widely used, so CGNAT continues to be an important transition technology.

Conclusion

CGNAT is an important technology that allows ISPs to conserve scarce IPv4 addresses by sharing public addresses among multiple subscribers. For ordinary browsing, email, streaming, and cloud applications, users may never notice it.

Problems become more visible when users require inbound Internet connectivity, such as port forwarding, CCTV access, self-hosted servers, game hosting, VPN servers, or direct remote access.

The key diagnostic clue is often:

Router WAN IPv4 ≠ Internet-visible IPv4

particularly when the router's WAN address falls within:

100.64.0.0/10

If CGNAT is confirmed, repeatedly changing port-forwarding, DMZ, UPnP, or DDNS settings on the local router will generally not remove the upstream NAT. The practical solution is usually to obtain a public IPv4 address from the ISP or use an alternative architecture such as IPv6, a secure overlay network, reverse tunneling, or a VPS-based tunnel.

For businesses requiring predictable inbound connectivity, VPN access, CCTV, or hosted services, a properly secured static public IP connection remains one of the most straightforward options.

Technical References

The core CGNAT Shared Address Space is standardized by RFC 6598, while common behavioral requirements for Carrier-Grade NAT systems are documented in RFC 6888.

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