Double NAT and bridge mode

Apple Support told me to just choose "Ignore," which I did. However I am concerned about ignoring this. Can there be problems caused by ignoring the Double NAT?

Yes, there can be problems running your network with a Double NAT condition.....some folks call this an error....such as slower browsing, or no browsing in severe cases, or more commonly......some websites load fine while others are slow or won't load at all.

If you are trying to use Back to My Mac or configure port mapping on your network router, the Double NAT will probably not allow the service to operate correctly.

On the other hand, sometimes you can get away with a Double NAT condition on a simple network. If things seem to work OK, and you don't notice any problems on the network, then you really can probably "ignore" the condition.

But frankly, you would want to avoid a Double NAT error if possible, since I cannot think of any advantage for running a Double NAT network condition if it can be avoided in the first place.

Unfortunately, you are receiving conflicting information from Apple. Apple's own AirPort Utility software is telling you to avoid the Double NAT by running the AirPort in Bridge Mode. Yet, it appears as if Apple Support has (surprisingly) told you to "ignore" the Double NAT condition or error.

The bottom line perhaps.....your AirPort will run more efficiently if you run it in Bridge Mode.

The primary issue will be that your network will not be running efficiently as any data to/from the Internet will have to traverse through two NAT routers unnecessarily. This will significantly reduce the data throughput performance, especially for streaming from the Internet.

The is no real security risk by disabling one or the other device's NAT service. NAT is not a true "firewall."

Same here, generally. Double NAT created two problems for me: file permissions were corrupted due to mixed routing to iCloud; also, Internet connections were intermittent. A singe simple network can only use one DHCP service at a time. With ISP help, logged into modem with private ip 192.168.0.1 and used modem's particular control panel to pass-through a selected plugged in modem port connected to Apple Airport router. You know that modem router is at least partly shut down if you can't login to 192.168.0.1 again :-)...

That was just the beginning. Then called Apple support to help configure a few Airport routers using Apple Airport Utility. Definitely, modem's router must be turned off to use Airport router. Otherwise, turn off Apple Airport router by bridging it, take your chances with whatever else? Well, that depends. Read on.

That's how-to for the simple Americas' network. Australasia, very different: simply bridge the Airport and government compliant services automatically shut down modem routing, then transfer to Airport WiFi. Parts of Texas and Yukon, different ecosystems apply. Enjoy the nature... it's a wild world.

I am using Airport Express and an Ooma VOIP. After updating to the latest Airport firmware, Airport Utility Status showed an amber light and Double NAT which I believe is due to the Ooma.

Ooma says it should connect between your main modem and router.. but in reality it is a really low end router and is totally unsuitable for most people in this position.. although it does depend on your internet speed.. for slow speed like ADSL the Ooma is probably just good enough. The Express is no powerhouse either btw..

If you have decent speeds swap them around.. put the Express in front as the main router and plug the Ooma into the Express.. you might then need to forward ports.. which can be tricky.. but the Express includes a special service called Default Host.. on the Network options tab.. this is equivalent to DMZ on most routers.. set the Ooma to a static IP in the Express or on the Ooma itself.. and place it as default host.. this will enable all ports.. so incoming calls which are the big problem should get through without issues.