The NETGEAR Nighthawk CAX80 is a cable modem and Wi-Fi 6 router in one box, so a double NAT arises when you plug a second router, a mesh system or another gateway behind it, and the second device also performs routing. The symptoms are strict NAT types on consoles, port forwards that never work, trouble with remote access and the odd call or game that complains of two layers of translation. NETGEAR's own support article on problems caused by a router connected to an ISP gateway describes the fix:
The checks in more detail
either put the first device in bridge mode, or put the second router in access point mode, and the guide says to turn off the gateway's Wi-Fi if you use another router's Wi-Fi. For the CAX80, the second option is the usual one, because the CAX80 is both the modem and the first router, and it has no simple modem-only switch for most owners. Put the router or mesh system behind it into access point or bridge mode, so that it passes traffic and the CAX80 does the routing. Check how you have connected things.
The second router's WAN, or internet, port should connect to one of the CAX80's LAN ports. If you intend to use the second router as the main router, check whether the CAX80 offers an option to turn off routing, or whether your cable provider can supply a bridge mode for the account. Not everything needs to change: search results note that double NAT has little effect on ordinary browsing and streaming, and it matters mostly for gaming and hosting. Test your NAT type on a console and a port forward.
In an eero set-up, eero's own help explains that you can put the eero into bridge mode, which makes the CAX80 the router, at the cost of the eero's own security and some app features. Turn off one of the two Wi-Fi networks to stop devices roaming between them. After the change, restart the modem first and then the second router, and look at the second router's WAN address, which should now be the CAX80's private LAN address, with the CAX80 holding the public one. If the provider has to change the CAX80's mode, ask them.
Differential
Likely causes of “NETGEAR Nighthawk CAX80 cable modem router shows double NAT or strict NAT”, and how to tell them apart
- 1
A second router doing routing
What separates it Strict NAT or failed port forwards
How to confirm Put the second router in access point or bridge mode
- 2
Two Wi-Fi networks
What separates it Devices roam between them
How to confirm Turn one off
- 3
The second router's WAN on the wrong port
What separates it Odd results
How to confirm Connect to a CAX80 LAN port
- 4
An eero in router mode
What separates it The app reports double NAT
How to confirm Use bridge mode on the eero
- 5
No change possible on the CAX80
What separates it The provider locks features
How to confirm Ask the provider
Before you touch a setting
Record this first — changing settings destroys the evidence
- The second router and its mode
- The NAT type on a console
- The WAN address of the second router
- The provider's options
Try in this order
0 of 6 completedFind the second router
ReversibleAnd its mode.
Set access point or bridge mode
ReversibleOn the second device.
Connect to a LAN port
ReversibleOn the CAX80.
Turn off one Wi-Fi network
ReversibleTo avoid roaming.
Restart modem then router
ReversibleAnd recheck.
Test NAT type
ReversibleAnd a port forward.
Model-specific
What is true of this model and not of its siblings
- Modem and router
- The CAX80 is both in one box.
- Access point mode
- It stops the second device routing.
Stop boundary
When this stops being a self-service repair
- !If the CAX80's mode cannot be changed, ask the provider
- !If NAT stays strict after the change, test a port forward
- !Remember double NAT has little effect on browsing
Evidence ledger
Sources behind this answer
NETGEAR's guide to double NAT with an ISP gateway.
CAX80 owners with speeds far below plan.
How owners clear a double NAT on an eero.
Bridge mode and double NAT on an eero network.
Exact questions
Common questions
Why do I have double NAT on my CAX80?+
A second router is also routing.
How do I fix it?+
Put the second router in access point or bridge mode.
Does it slow browsing?+
Not noticeably.
When does it matter?+
For gaming and hosting.