Compare your router’s WAN IPv4 address with the public IPv4 address seen from a device on the same connection. If they differ, another routing or translation layer is upstream—but that alone does not tell you whether it is your ISP’s CGNAT or another router. Check the WAN address range and identify the equipment between your router and the internet. CGNAT describes where translation happens; double NAT describes two translation layers, which may be in your home, at your ISP, or both.
What CGNAT and double NAT mean
CGNAT is about who operates the NAT
Carrier-grade NAT (CGNAT) is network address translation performed within an internet service provider’s network. It often lets multiple subscribers share a public IPv4 address. The IETF’s RFC 6598, published in April 2012, designates 100.64.0.0/10 as Shared Address Space to accommodate carrier-grade NAT devices.
Double NAT is about the number of translation layers
Double NAT means a connection passes through two NAT layers. Both may be routers in your home, or one may be your router and the other the ISP’s CGNAT. The term does not, by itself, identify who operates the upstream layer.
How to check whether you have CGNAT or another upstream router
- Find your router’s WAN IPv4 address. Sign in to the router that connects your network to the internet and open its Internet, WAN, or status page. Menu labels vary by manufacturer; Zyxel’s guidance uses the router’s web interface and WAN status page.
- Check the externally visible IPv4 address. From a device using that same internet connection, use an external IP-checking service. Compare IPv4 with IPv4: a website may show an IPv6 address, which is not a like-for-like comparison.
- Compare the two addresses. If the WAN IPv4 and external IPv4 differ, an upstream routing or translation boundary exists. The mismatch does not reveal whether that boundary is an ISP CGNAT gateway, an ISP-supplied modem/router, or another router in your home.
- Check the WAN address range and upstream equipment. A WAN address in 100.64.0.0/10 is strong evidence of carrier-side NAT. An RFC 1918 private address also means the router is not directly assigned a public IPv4 at that interface, but it could have been assigned by an upstream home router or an ISP device. Trace the cabling and check the upstream gateway’s WAN status, or ask your ISP to identify the boundary.
- Interpret a match carefully. If the WAN IPv4 matches the externally visible IPv4, the checked router has a public IPv4 address and no intervening IPv4 translation is apparent at that point. That does not rule out another NAT inside the home, or prove that a particular port is reachable through firewall rules.
Zyxel’s CGNAT guidance describes the WAN-versus-public-IP comparison as a first check. It is useful for locating a discrepancy, not as a stand-alone way to identify who controls the upstream network.
The Tool Desk
Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →#1 Best Overall
- DUAL-BAND WIFI 6 ROUTER: Wi-Fi 6(802.11ax) technology achieves faster speeds, greater capacity and reduced network congestion compared to the previous gen. All WiFi routers require a separate modem. Dual-Band WiFi routers do not support the 6 GHz band.
- AX1800: Enjoy smoother and more stable streaming, gaming, downloading with 1.8 Gbps total bandwidth (up to 1200 Mbps on 5 GHz and up to 574 Mbps on 2.4 GHz). Performance varies by conditions, distance to devices, and obstacles such as walls.
- CONNECT MORE DEVICES: Wi-Fi 6 technology communicates more data to more devices simultaneously using revolutionary OFDMA technology
- EXTENSIVE COVERAGE: Achieve the strong, reliable WiFi coverage with Archer AX1800 as it focuses signal strength to your devices far away using Beamforming technology, 4 high-gain antennas and an advanced front-end module (FEM) chipset
- OUR CYBERSECURITY COMMITMENT: TP-Link is a signatory of the U.S. Cybersecurity and Infrastructure Security Agency’s (CISA) Secure-by-Design pledge. This device is designed, built, and maintained, with advanced security as a core requirement.
Clues that distinguish the two cases
| Diagnostic question | Likely customer-side double NAT | Likely carrier-side CGNAT |
|---|---|---|
| Where is the extra translation? | Another modem/router or router you control is operating in router/NAT mode. | Translation takes place in the ISP network, outside your control. |
| What might the first router’s WAN address show? | Often a private address assigned by an upstream home or ISP gateway. | It may be in 100.64.0.0/10 or another non-public range assigned upstream. |
| Who can change the extra NAT? | Usually the administrator of the upstream device, if its settings support bridge, passthrough, or access-point operation. | The ISP controls the carrier translation; ask about public IPv4 or supported alternatives. |
| What is the useful next step? | Identify both routing devices, then change the intended device’s mode or configuration. | Confirm with the ISP and ask about inbound-access options. |
These are diagnostic tendencies, not guarantees based on an IP address alone. An ISP-managed gateway may sit in your home, and some providers use non-RFC 6598 addresses internally.
Why it matters for port forwarding and remote access
With CGNAT, unsolicited inbound IPv4 connections may not reach your home router because the public-facing translation is controlled by the ISP. A port-forwarding rule on your router cannot configure that ISP-side NAT. If you need remote access, hosting, or an inbound VPN, ask your provider whether it offers a public IPv4 address, whether it is static or dynamic, and what eligibility, price, or other conditions apply; those terms vary by provider, location, and plan.
Rank #2
- Dual-band Wi-Fi with 5 GHz speeds up to 867 Mbps and 2.4 GHz speeds up to 300 Mbps, delivering 1200 Mbps of total bandwidth¹. Dual-band routers do not support 6 GHz. Performance varies by conditions, distance to devices, and obstacles such as walls.
- Covers up to 1,000 sq. ft. with four external antennas for stable wireless connections and optimal coverage.
- Supports IGMP Proxy/Snooping, Bridge and Tag VLAN to optimize IPTV streaming
- Access Point Mode - Supports AP Mode to transform your wired connection into wireless network, an ideal wireless router for home
- Advanced Security with WPA3 - The latest Wi-Fi security protocol, WPA3, brings new capabilities to improve cybersecurity in personal networks
What to do when the extra NAT is in your home
If an upstream router you control is creating the second NAT layer, you may be able to configure one device to stop routing. Depending on the equipment and ISP instructions, options include placing a supported modem/router in bridge or IP-passthrough mode, or configuring a device to act only as an access point.
Bridge or passthrough mode changes how the device handles routing, so follow the manufacturer’s and ISP’s instructions and check model, firmware, and service compatibility. Zyxel explains these modes for supported FWA devices in its router-mode and bridge/IP-passthrough guidance. Removing a customer-side NAT layer does not remove CGNAT operated by the ISP.
Rank #3
- NIGHTHAWK WIFI 6 ROUTER FOR YOUR WHOLE HOME: Delivers fast, reliable WiFi across every room of your apartment or small home for streaming, gaming, video calls, and smart home devices, all running at the same time without slowing each other down.
- WORKS WITH YOUR EXISTING INTERNET SERVICE: Pairs with your existing modem or gateway via ethernet. Compatible with most cable, fiber, DSL, and satellite providers. Some gateways and modem router combos may require bridge mode. No coax needed.
- SET UP AND MANAGE YOUR NETWORK WITH THE NIGHTHAWK APP: Download the free Nighthawk app on iOS or Android for guided setup. Manage WiFi, run speed tests, pause devices, and set up guest networks from anywhere. Active internet required.
- READY FOR THE DEVICES YOU ALREADY OWN: Your phones, laptops, and TVs work right out of the box. WiFi 6 delivers speeds up to 1.8 Gbps across 2.4 GHz and 5 GHz bands. Backward compatible with WiFi 5 and earlier.
- COVERAGE IN EVERY ROOM: Covers up to 1,500 sq. ft. for up to 20 connected devices. Walls, floors, and interference can reduce range. Larger or multi-story homes may benefit from a NETGEAR Orbi mesh WiFi system.
When IPv6 may help
IPv6 may be an alternative for inbound connectivity if your ISP and equipment support it. It still requires appropriate routing and firewall configuration, so enabling IPv6 is not an automatic fix for remote access.
Quick Recap
Best Value
- Dual band router upgrades to 1200 Mbps high speed internet (300mbps for 2.4GHz plus 900Mbps for 5GHz), reducing buffering and ideal for 4K stream
- Full Gigabit Ports - Gigabit Router with 4 Gigabit LAN ports, ideal for any internet plan and allow you to directly connect your wired devices
- Boosted Coverage - Four external antennas equipped with Beamforming technology extend and concentrate the Wi-Fi signals
- MU-MIMO technology - (5GHz band) allows high speeds for multiple devices simultaneously
- Access Point Mode - Supports AP Mode to transform your wired connection into wireless network, an ideal wireless router for home
Rank #4
- 𝐅𝐮𝐭𝐮𝐫𝐞-𝐏𝐫𝐨𝐨𝐟 𝐘𝐨𝐮𝐫 𝐇𝐨𝐦𝐞 𝐖𝐢𝐭𝐡 𝐖𝐢-𝐅𝐢 𝟕: Powered by Wi-Fi 7 technology, enjoy faster speeds with Multi-Link Operation, increased reliability with Multi-RUs, and more data capacity with 4K-QAM, delivering enhanced performance for all your devices.
- 𝐁𝐄𝟑𝟔𝟎𝟎 𝐃𝐮𝐚𝐥-𝐁𝐚𝐧𝐝 𝐖𝐢-𝐅𝐢 𝟕 𝐑𝐨𝐮𝐭𝐞𝐫: Delivers up to 2882 Mbps (5 GHz), and 688 Mbps (2.4 GHz) speeds for 4K/8K streaming, AR/VR gaming & more. Dual-band routers do not support 6 GHz. Performance varies by conditions, distance, and obstacles like walls.
- 𝐔𝐧𝐥𝐞𝐚𝐬𝐡 𝐌𝐮𝐥𝐭𝐢-𝐆𝐢𝐠 𝐒𝐩𝐞𝐞𝐝𝐬 𝐰𝐢𝐭𝐡 𝐃𝐮𝐚𝐥 𝟐.𝟓 𝐆𝐛𝐩𝐬 𝐏𝐨𝐫𝐭𝐬 𝐚𝐧𝐝 𝟑×𝟏𝐆𝐛𝐩𝐬 𝐋𝐀𝐍 𝐏𝐨𝐫𝐭𝐬: Maximize Gigabitplus internet with one 2.5G WAN/LAN port, one 2.5 Gbps LAN port, plus three additional 1 Gbps LAN ports. Break the 1G barrier for seamless, high-speed connectivity from the internet to multiple LAN devices for enhanced performance.
- 𝐍𝐞𝐱𝐭-𝐆𝐞𝐧 𝟐.𝟎 𝐆𝐇𝐳 𝐐𝐮𝐚𝐝-𝐂𝐨𝐫𝐞 𝐏𝐫𝐨𝐜𝐞𝐬𝐬𝐨𝐫: Experience power and precision with a state-of-the-art processor that effortlessly manages high throughput. Eliminate lag and enjoy fast connections with minimal latency, even during heavy data transmissions.
- 𝐂𝐨𝐯𝐞𝐫𝐚𝐠𝐞 𝐟𝐨𝐫 𝐄𝐯𝐞𝐫𝐲 𝐂𝐨𝐫𝐧𝐞𝐫 - Covers up to 2,000 sq. ft. for up to 60 devices at a time. 4 internal antennas and beamforming technology focus Wi-Fi signals toward hard-to-reach areas. Seamlessly connect phones, TVs, and gaming consoles.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
