Will 'Double NAT' cause any problems for me?

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Level 1

21 points

Will 'Double NAT' cause any problems for me?

Hi there

I have just received a Netgear VMDG280 Cable/ DSL modem/wireless router from Virgin Broadband in the UK and I plugged it into my Airport Extreme 802.11n base station. The internet works fine but the amber light remains flashing, warning me of a Double Nat error.

I can easily select for my Airport to 'ignore' this Double NAT error message, but am worried that by ignoring this warning, I might compromise something important in my whole broadband set up. Could it also reduce security etc?

Essentially, Im not doing anything fancy with my wireless network, besides running a Macbook Pro, Iphone, Ipad and friend's laptops etc.

With Double NAT existing on my network, will this affect the service I will receive in any way? Or can I just put it out of my mind?

Many thanks

Dan

MacBook Pro 17 Inch

Posted on Sep 18, 2010 3:14 AM

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Answer 1

Bob Timmons

Level 10

185,120 points

Sep 18, 2010 6:24 AM in response to lorddlm2

Welcome to the discussions, Dan!

You have two routers in series there and the Double NAT error indicates that both devices are trying to handle DHCP (give out IP addresses) and NAT (Network Address Translation). The Double NAT can cause difficulties if you add more devices and it can potentially slow down communications on your network.

You only want one router handling the DHCP and NAT functions on a network, so my suggestion would be to configure the AirPort Extreme as a "bridge" so that it functions correctly on the network.

Open AirPort Utility - Click Manual Setup
Click the Internet icon
Set the Connection Sharing setting to "Off (Bridge Mode)"
Click Update to save your settings

You should have a green light on the AirPort Extreme in 20-25 seconds.

Message was edited by: Bob Timmons

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Answer 2

lorddlm2 Author

Level 1

21 points

Sep 18, 2010 6:36 AM in response to Bob Timmons

Hi there Bob

Thank you so much for your reply.

If I operate Airport Extreme in Bridge mode, will that mean that the technical quality and security of the Airport Extreme base will be bypassed in favour of the Netgear? As you can tell, Im a total novice at this but it would seem that if the Netgear is classed as the lesser device of the two, shouldnt the Airport Extreme handle the more important tasks rather than being a passive 'bridge'?

That said, once I set up the AE as a bridge, are there any additional security or performance settings that I then need to adjust in the Airport Admin Utility?

Thank you so much for taking the time to respond to me

Dan

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Answer 3

Bob Timmons

Level 10

185,120 points

Sep 18, 2010 7:10 AM in response to lorddlm2

+If I operate Airport Extreme in Bridge mode, will that mean that the technical quality and security of the Airport Extreme base will be bypassed in favour of the Netgear?+

No

+if the Netgear is classed as the lesser device of the two, shouldnt the Airport Extreme handle the more important tasks rather than being a passive 'bridge'+

The Netgear is already configured as the "main" router on your network. It is what we call a "gateway", a combination modem and router on the same chassis. The AirPort Extreme does not include a modem, so if you wanted to make it the "main" router on your network, you would need to purchase a separate stand alone modem and then set up the Netgear as a "bridge". That gets really complicated.

If you are seeing no adverse effects of the Double NAT, you can choose to "ignore" the message and the light will turn green. If you want to do this, open AirPort Utility, click Manual Setup, and then click on the word "Status" on the summary page. Click "ignore" regarding the Double NAT.

Networking rules specify that you should try to avoid the Double NAT situation if possible. On a simple home network this is not usually a serious error, but it can slowdown internet browsing. If you plan to add a gaming console and want to play online games with other people, then the Double NAT will probably prevent you from doing so.

My suggestion to place the AirPort Extreme in bridge mode was just that...a suggestion. If you are happy with the performance of your network now and simply want to get the light to turn green, you can choose to "ignore" the message.

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Answer 4

lorddlm2 Author

Level 1

21 points

Sep 18, 2010 7:48 AM in response to Bob Timmons

Hi there Bob

Thank you so much for explaining all this. I will definitely follow your advice and 'Bridge' the Airport Extreme. As I mentioned before, are there any additional security or performance settings that I then need to adjust in the Airport Admin Utility when setting it in Bridge mode?

Thank you again for all your help

Dan

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Answer 5

Bob Timmons

Level 10

185,120 points

Sep 18, 2010 8:03 AM in response to lorddlm2

+As I mentioned before, are there any additional security or performance settings that I then need to adjust in the Airport Admin Utility when setting it in Bridge mode?+

No other adjustments necessary. You only need to change the configuration to "bridge mode".

Message was edited by: Bob Timmons

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Answer 6

lorddlm2 Author

Level 1

21 points

Sep 18, 2010 8:17 AM in response to Bob Timmons

Thank you so much Bob

Dan

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Answer 7

cyvi937

Level 1

104 points

Sep 18, 2010 8:17 AM in response to lorddlm2

You should turn off your Netgear router's wireless capabilities. Otherwise, you'll have two wireless networks running which could interfere with each other.

Also: running an AirPort Extreme in bridge mode means you can't use its guest network feature. If you really want to use this feature, you'll have to find a way of putting your Netgear router into bridge mode instead of the Extreme.

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