Airport Extreme as router for Netgear 300N

As you may have already guessed, the correct and best setup would have the Netgear 300N configured to act only as a simple modem. If what you say is correct.....and the Netgear device does not provide a "modem only" option, then there is not much else that can be done in that regard.

If the Guest Network feature is important to you, a better option....if possible....would be to replace the Netgear 300N with a simple ADSL modem. This would allow you configure the AirPort Extreme correctly to provide DHCP and NAT services for the network.

The least desirable option in terms of a correct setup, would be to try to run the network with the Double NAT error.....which can possibly create some unpredictable issues on the network such as slow browsing, intermittent loss of some websites (while others load correctly), and communication errors between any devices that are connected to the AirPort versus devices connected to the Netgear modem/router.

Online gaming consoles hate Double NAT, so it will be difficult, if not impossible to play interactively online if that is a requirement for your network. Likewise, port forwarding....if required by devices on your network....will be destroyed by Double NAT

The bottom line.....sometimes you can get away with a Double NAT error on a simple home network.....and sometimes it is a deal killer. It's just not possible for us to predict how the error might affect your network.

One simple test that you might want to perform to see if the Double NAT settings will "stick".....is to power off the AirPort Extreme by pulling the power cord, wait a minute, then power up the AirPort Extreme again. Sometimes, the AirPort will start back up in Bridge Mode, so you will have to be on the lookout after a power outage. A firmware update can also encourage the AirPort to start up in Bridge Mode if AirPort Utility senses that it would be the correct setup.

We don't recommend that users run their networks with Double NAT if it can be avoided, but the decision is up to you.

If your Netgear cannot be bridged.. some supplied by the ISP can be bridged if you ring your ISP who remotely connect.

Buy a cheap modem.. it does depend a bit on your line and how far from the exchange you are. TP-Link modems like 8950N or 8960N bridge easily. They are less than $50 here.. might be cheaper in the US.

I would also look up bridge DGN2000 or DGN2200 whichever is the exact model of your netgear as instructions are often available albeit hidden.

The setup requires you to use PPPoE. That is the only way your Airport can connect to a bridged ADSL modem. So your ISP must support it.

You do not use your credentials in the modem. That is used in the Airport WAN setup for pppoe.

Can anyone confirm that modem only function is same as bridge mode?

There is a lot of confusion about what "bridge mode" might be, and no assurance that bridge mode is modem only mode. You would need to confirm with your ISP for your specific device.

If simple adsl modem becomes available, is there some config required?

Yes, you must reset the AirPort Extreme back to factory default settings and then set it up to work with the new modem. The same would be true if you are able to configure your modem/router to function as a simple modem.

Eg will I need to tell it the PPPoA, PPP User ID and Password?(seems likely)

The AirPorts use PPPoE authentication. If your ISP requires PPPoA, then you will need a special modem that will adapt PPPoA to PPPoE. This is one example....(not necessarily a recommendation)...... of a product that will do this:

Vigor 120 ADSL Modem - Draytek

You should check with your current Internet Service Provider though, before you do anything, to make sure that they will support your new setup.

Or just plug in and configure the Airport Extreme?

Unfortunately, things are never quite that easy.

What is the exact model number of the Netgear?

Looking up at the top of the post, the OP mentions in the title that he has a Netgear 300N, so one would assume that this is the model that he has.

N300 Wireless Gigabit Router Setup Manual - Netgear

I may be mistaken, but I think this is what he is referring to http://www.netgear.com/home/products/networking/dsl-modems-routers/dgn2200.aspx

There is some client isolation stuff in the manual, which may have been setup, so it does segmentation of traffic. The Prime and Guest network, are client isolated, AFAIK.

I would also suggest checking if Guest Network packets make it to the N300.

Thanks....interesting. A quick Google search for Netgear 300N produced this link.........N300 Wireless Gigabit Router Setup Manual - Netgear

Hopefully, the OP will clarify.

Current Netgear config is PPPoA. The Extreme seems to handle it OK.

I am not aware of any settings on the AirPort Extreme versions that would allow PPPoA authentication, but there are settings for PPPoE on all versions of the AirPort Extreme.

Maybe you mean that the Netgear is connecting to the ISP using PPPoA? In that case, the Extreme would be connecting to the Netgear using Ethernet....either DHCP or Static depending on how you have things set up.

If it were possible to configure the Netgear to operate as only a modem, and your ISP requires PPPoA to authenticate, then you will still need another device to allow the AirPort to connect.....since it cannot provide PPPoA credentials.

Thanks for the additional information. I will refer to the screens in the iOS version of AirPort Utility from this point on, unless you indicate otherwise.

I understand that your Netgear modem/router is establishing the Internet connection through your ISP using PPPoA authentication....and....that the Netgear is configured to act as a router for your network.

If you start over and open up AirPort Utility on the iPhone/iPad screen, tap on the AirPort Extreme picture or icon, then tap Edit, then tap Internet Connection......I believe that you will see that DHCP is highlighted, which indicates that the AirPort Extreme is currently connecting to the Netgear modem/router using an Ethernet connection, and also that the AirPort Extreme is receiving an IP address from the Netgear router automatically using DHCP.

Static and PPPoE are lighter colored boxes....since they are connection types that are in not in use at the present time.

Further down the page, you will see the IP address that the Negear router has assigned to the AirPort Extreme.....likely something like 192.168.1.x.....Subnet Mask, Router Address and other boring stuff like DNS Server addresses.

Is this what you see? If yes, this indicates that the AirPort Extreme is not using a PPPoE type connection to connect to the Netgear modem/router. Your screen should look like this...with different IP addresses, etc:

Now....please forgive me....but I am not sure what the actual question is at this point. If you were perhaps thinking that the AirPort Extreme was using a PPPoE type connection, it is not. Is that the question? Or, is there another?

Since the AirPort Extreme is receiving its settings from another router......it would be normal to see only one value in the DNS field.

If the AirPort Extreme were connected directly to a modem.....and the AirPort Extreme was initiating the Internet connection......as mine is....then you would normally see values in both DNS fields....since most ISPs provide two DNS server settings as part of the regular Internet connection process.