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Compare your router’s WAN IPv4 address with the public IPv4 address visible from a device on the same connection. If they differ, an upstream routing or NAT layer may be involved—but that alone does not prove your ISP is using CGNAT. A WAN address in 100.64.0.0/10 is a stronger clue: the IETF reserves that range for shared use in service-provider networks. Check for another router or ISP gateway, then ask your ISP to confirm the setup if it affects what you need to do.
Compare your router’s WAN IPv4 with your public IPv4
Use an IPv4 lookup from a device connected to the internet service you want to check, then compare its result with the IPv4 address assigned to the router’s WAN or Internet interface. Both values must be IPv4 and must be checked on the same connection. A device’s local address—often something like 192.168.x.x—is not the WAN address and is not the value to compare.
- Connect directly to the network you’re checking. Temporarily turn off a VPN, proxy, or other relay; otherwise the lookup may show the relay’s address rather than the connection’s.
- Find the router’s WAN address. Sign in to the router or modem-router and open its status or internet-connection page. Look for a label such as WAN IPv4, Internet IPv4, or Internet address. Interface names and locations vary by device.
- Look up the public IPv4 address. From a device on that same connection, use a service that explicitly shows IPv4. If the result displays only IPv6, it cannot be compared with the router’s IPv4 address.
- Compare the two values. A match means the router is using the observed public IPv4 for its WAN connection at that moment. A mismatch means the address seen outside differs from the address on that router’s WAN interface; investigate the network layout before attributing the difference to the ISP.
- Check for another gateway or router. An ISP-provided modem-router, mesh system, or customer-owned router between the internet connection and the device you checked can create an additional routing or NAT layer.
- Check whether the WAN address is in 100.64.0.0/10. This range runs from 100.64.0.0 through 100.127.255.255. A WAN address inside it strongly points to shared addressing in a provider network.
Interpret the result without mistaking a clue for proof
| What you find | What it indicates | What to check next |
|---|---|---|
| WAN IPv4 is in 100.64.0.0/10 | Strong evidence of provider-side shared addressing. The IETF set this range aside for service-provider networks; it is not globally routable. RFC 6598 | Ask your ISP whether the address is part of its CGNAT arrangement and what connectivity options your plan supports. |
| WAN IPv4 differs from the public IPv4 lookup | Consistent with translation or routing upstream of the checked router, but it does not identify who operates that layer. RFC 6598 | Look for an ISP gateway, mesh router, or second router between the internet and the checked router. |
| WAN IPv4 is in an RFC 1918 private range | The WAN interface is not directly assigned a globally routable IPv4 address. The address alone does not distinguish a local gateway from a provider network. RFC 6598 | Trace the equipment between your router and the service connection, then ask the ISP to identify the upstream address. |
| WAN IPv4 matches the public IPv4 lookup | This weakens the case for an additional IPv4 NAT layer upstream of that router at the time of the check. | Do not assume inbound connections are allowed; router firewalls and ISP filtering can still affect them. |
| Port forwarding does not work | Not a stand-alone CGNAT test. A forwarding rule, firewall, TCP/UDP selection, inactive service, or another NAT layer may be responsible. RFC 6269 | Verify the service and forwarding configuration, and use the WAN/public IPv4 comparison to investigate the network path. |
Why CGNAT can affect inbound connections
Carrier-grade NAT (CGNAT) lets a provider share public IPv4 address capacity among subscribers. RFC 6598 defines a dedicated shared IPv4 block for service-provider use, including links between CGN equipment and customer-premises equipment. The IETF describes CGN as an interim way to extend IPv4 use while providers deploy IPv6 solutions in RFC 9099.
If the provider translates connections upstream of your home router, a port-forwarding rule on that router cannot by itself create the matching inbound mapping on the provider’s network. For hosting a service or reaching home equipment remotely, establish which device or network layer owns the upstream address and ask the ISP about available options. IPv6 may help only when the relevant service and endpoints support it.
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#1 Best Overall
Elebase USB to USB C Adapter for iPhone 18 Pro Max,USBC Car Charger Adapter
- Read Before You Buy — No Video Output: These adapters support charging and USB 2.0 data transfer, but cannot transmit video signals. Except for standard USB webcams (which use USB data only), they are not compatible with HDMI/DisplayPort cables, video-capable USB-C hubs, or docking stations with video output.
- Convert USB-A Ports to USB-C: Designed to connect USB-C earphones, cables, flash drives, card readers, and other USB-C accessories to standard USB-A ports. Plug-and-play with no drivers or software required.
- Aluminum Alloy Housing: Built with a sturdy aluminum alloy shell that aids in heat dissipation and protects against daily wear and scratches. Designed to maintain a stable and secure connection.
- Compact & Travel-Friendly: The ultra-compact design allows the adapter to stay plugged into your device without blocking adjacent ports or adding bulk, reducing wear and tear on your original USB ports.
- 12-Month Warranty: Backed by a 12-month manufacturer warranty for peace of mind. Designed to meet strict quality control standards for reliable everyday performance.
Ask your ISP to confirm the arrangement
A public-IP lookup reveals the address seen from outside, not which device performed translation. When the distinction matters, ask the provider directly:
- “Is this connection behind CGNAT?”
- “Is the WAN address assigned to my router a public IPv4 address, or an upstream shared or private address?”
- “Can this plan receive a public IPv4 address, or provide IPv6 connectivity suitable for my use?”
Availability and terms vary by provider, plan, and location; no specific ISP offer or eligibility can be inferred from these checks.
Quick Recap
Bestseller No. 5
Best Value
Anker USB C Hub, 5-in-1 USBC to HDMI Splitter with 4K Display
- 5-in-1 Connectivity: Equipped with a 4K HDMI port, a 5 Gbps USB-C data port, two 5 Gbps USB-A ports, and a USB C 100W PD-IN port. Note: The USB C 100W PD-IN port supports only charging and does not support data transfer devices such as headphones or speakers.
- Powerful Pass-Through Charging: Supports up to 85W pass-through charging so you can power up your laptop while you use the hub. Note: Pass-through charging requires a charger (not included). Note: To achieve full power for iPad, we recommend using a 45W wall charger.
- Transfer Files in Seconds: Move files to and from your laptop at speeds of up to 5 Gbps via the USB-C and USB-A data ports. Note: The USB C 5Gbps Data port does not support video output.
- HD Display: Connect to the HDMI port to stream or mirror content to an external monitor in resolutions of up to 4K@30Hz. Note: The USB-C ports do not support video output.
- What You Get: Anker 332 USB-C Hub (5-in-1), welcome guide, our worry-free 18-month warranty, and friendly customer service.
Rank #4
Sale
UGREEN USB to USB C Adapter Combo 4-Pack, 10Gbps USB C Converter Space Gray
- Dual Converters, Infinite Potential：Includes 2× USB C male to USB A female adapters and 2× USB A male to USB C female adapters. Perfect for a wide range of uses—tablets with Bluetooth keyboards, expand USB ports on macbook, and more. Two different converters for all your daily needs
- Next-Level 10Gbps & 3A Charging: No more slow 480Mbps, this usb to usb c adapter has a transfer speed of up to 10Gbps, allowing you to do more transferring in less time. This usb adapter fits both USB A and USB C charger, supporting up to 3A fast charging
- Upgraded Exquisite Craftsmanship: With an aluminum alloy housing and metal connector, the usbc to usb adapter is extremely durable and sturdy. Rigorously tested to withstand more than 10,000 times of plugging and unplugging, ensuring long-lasting performance
- Broad Compatible: The usb c to usb adapter widely supports all USB C/ USB A devices like laptops, tablets, cellphones, car chargers, and phone chargers. Such as compatible with MacBook Pro/Air 2023/2022, Thunderbolt 4/3 Devices,Apple MagSafe Watch 9/8/7/SE/Ultra, iPad Pro 2022/2021, Samsung Galaxy S23/S20/S10, and iPhone 17/16/15 Pro. Plug and play
- Please Note: To reach 10Gbps speed, keep the cable under 3.3 ft. For USB A Male to USB C adapters, try flipping the USB C connector. USB C Male to USB A adapters support bidirectional 10Gbps transfer within 3.3 ft
Rank #3
Sale
Anker USB C Hub, 7in1 Multi-Port USB Adapter, 4K@60Hz USBC to HDMI Splitter
- Sleek 7-in-1 USB-C Hub: Features an HDMI port, two USB-A 3.0 ports, and a USB-C data port, each providing 5Gbps transfer speeds. It also includes a USB-C PD input port for charging up to 100W and dual SD and TF card slots, all in a compact design.
- Flawless 4K@60Hz Video with HDMI: Delivers exceptional clarity and smoothness with its 4K@60Hz HDMI port, making it ideal for high-definition presentations and entertainment. (Note: Only the HDMI port supports video projection; the USB-C port is for data transfer only.)
- Double Up on Efficiency: The two USB-A 3.0 ports and a USB-C port support a fast 5Gbps data rate, significantly boosting your transfer speeds and improving productivity.
- Fast and Reliable 85W Charging: Offers high-capacity, speedy charging for laptops up to 85W, so you spend less time tethered to an outlet and more time being productive.
- What You Get: Anker USB-C Hub (7-in-1), welcome guide, 18-month warranty, and our friendly customer service.
Rank #2
Anker USB-C Hub, 5-in-1 USB Hub for Laptops, 4K HDMI Multiport Adapter
- 5-in-1 USB-C Hub: Experience comprehensive connectivity featuring a Power Delivery input, two USB-A 2.0 ports, a USB-A 3.0 port, and an HDMI port. (Note: The USB-C power delivery input port is only for connecting an external wall charger to power your laptop and cannot power peripheral devices.)
- 90W Pass-Through Charging: Achieve optimal charging with 90W pass-through power to your laptop, supported by a total input of 100W, with the hub reserving 10W for operational efficiency. (Note: Wall charger not included.)
- Quick Data Transfers: Accelerate your productivity with rapid data transfers using a high-speed 5Gbps USB 3.0 port and two 480Mbps USB 2.0 ports.
- 4K HDMI Display: Enhance your visual experience with a hub capable of delivering 4K resolution at 30Hz in both mirror and extend modes. Please note that this hub is compatible with MacBook (macOS 12 and newer), Windows 10 and 11, ChromeOS, and laptops equipped with DP Alt Mode and Power Delivery. Note: This device is not compatible with Linux.
- What You Get: Anker USB-C Hub (5-in-1, 4K HDMI), welcome guide, 18-month warranty, and our friendly customer service.
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