AirPort Extreme - enforce dual band broadcast?

Question

AirPort Extreme - enforce dual band broadcast?

I have a hardware firewall with wireless network inside it, broadcast by an AirPort Express locked to 5Ghz 802.11n only. I decided to replace my AirPort Express with an AirPort Extreme so all my b / g devices could be brought inside the firewall too. Previously, b / g devices routed through the ADSL router modem, outside the hardware firewall.

I asked a number of Apple helpers in the store (no one really knew much about the tech side of the Extreme's functionality) about the dual band broadcast, to find out if it really does broadcast two seperate SSID's and networks. They confirmed, after going into the guru's out back, that it in fact does.

I have set up all 2.4Ghz protocols with one SSID and all 5Ghz traffic with another.

I have tested big downloads on both SSID's at the same time to see if in fact, it maintains the "two" networks on the different frequencies.

It does! Fantastic!

However, and this is what has really frustrated me, the MacBook Pro which is the only 5Ghz device on the network, of it's own accord, jumps across to the 2.4Ghz broadcast.

I deleted the 2.4Ghz from my Preferred Networks. Deleted all reference from my Keychain of the 2.4Ghz network. It keeps reappearing and my Mac keeps selecting it ??? I wouldn't have bought the Extreme if I'd have known it tries to be lazy and broadcast the least complicated, least strenuous network.

So my question is, without locking the broadcast to 802.11n only, as I have the b / g stuff using it now, force the Mac to only use the 5Ghz n broadcast?

Massive bonus points if someone can help

Thanks,

Matt.

Message was edited by: Matt NewBones

Message was edited by: Matt NewBones

Message was edited by: Matt NewBones

Message was edited by: Matt NewBones

MacBook Pro 2.53Ghz 500GB, 4GB, iPhone 3GS 32GB 4.3, Mac OS X (10.6.6)

Posted on Mar 20, 2011 4:42 AM

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Answer 1

Mar 20, 2011 6:47 AM in response to Matt NewBones

I wouldn't have bought the Extreme if I'd have known it tries to be lazy and broadcast the least complicated, least strenuous network.

Matt,

This sounds like you are thinking that the AirPort Extreme is making some kind of choice between the signal that it chooses to broadcast. It's not. It broadcasts both a 2.4 Hz and 5 GHz radio signal simultaneously at all times.

It's up the computer to choose the signal to which it connects based on a combination of signal strength, low noise and who knows what other factors.

Looking at the configuration of the AirPort Extreme using Manual Setup, how did you assign separate names to the 2.4 GHz and 5 GHz networks?

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Answer 2

Mar 20, 2011 10:27 AM in response to Bob Timmons

Bob, thanks for your response.

There is no question around the Extreme broadcasting 2 radio signals at the same time, realised in my download tests.

I should have chosen better wording and explained a little more also.

If I replace the word "broadcast" with "serve" you'll get a better understanding of what I am trying to conclude. It seems the Extreme will try to utilise one, common frequency where it can. If I have my MacBook connected over 5Ghz and then I connect my iPhone 3GS, two scenarios occur;

1. The 2.4Ghz is not available and does not show up in the available listed networks on the iPhone.
2. The iPhone connects, but my MacBook is then automatically switched over to the 2.4Ghz network.

Two possible reasons;

1. The Extreme is programmed to serve via the fewest possible broadcasts (lazy).
2. The Extreme, when allowing a device connect, interferes with its sibling broadcast, and finds that the other is the better option, switching everything across (not possible as they are different frequency ranges).

I note that, if scenario no.2 occurs, I can manually select my 5Ghz network again and reconnect, using 5Ghz for the MacBook and 2.4Ghz for the iPhone at the same time. I don't want to keep dong this and shouldn't have to.

So, how do I force the MacBook to stay connected to the 5Ghz n network? This isn't possible via the Extreme as the closest setting is 802.11n only (5Ghz) - 802.11n only (2.4Ghz).

In response to your question, Bob, when clicking Wireless Network Options... from the Wireless tab, tick the 5Ghz Network Name box and rename it.

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Answer 3

Mar 20, 2011 11:14 AM in response to Matt NewBones

Thanks for the additional info. Try as I might, I cannot duplicate your issue of "switching" frequencies. The MacBook Pro stays solidly on 5 GHz while my older iPhone stays on the 2.4 GHz network. I've tried this using the same SSID for both bands and also using a separate name for the 5 GHz network.

If turn off my other wireless access points and cut the network down to only the AirPort Extreme as a test, my MBP will stay connected to 5 GHz until I'm down the hall with several walls acting as obstructions to the signal. Then the MBP will switch over to 2.4 GHz, which is normal, as the higher frequency signals are absorbed more quickly than 2.4 GHz signals and the MBP will look for the stronger signal, not necessarily the faster signal to connect.

If you go into AirPort Utility - Manual Setup and click the Wireless tab, what Wireless Radio Mode are you using for your network?

In this regard, we've seen a number of reports from users who state that they, like me, literally have to have close to a line-of-sight relationship between the computer and router when using 5 GHz.

I don't know if that is entering into your situation or not, but would be something to consider if the router is few rooms away.

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Answer 4

Mar 20, 2011 11:46 AM in response to Bob Timmons

No way, strange, I hope I don't have a faulty device then. I only purchased it yesterday.

In response to the line of site query, I am about 3 metres from the Extreme in the same room. I could literally take 5 - 6 steps and touch it. Good call on the range distance capabilities of the two different frequencies, but I don't think that's it.

Interestingly, addressing the possibility of interference, all other networks from the neighbours are 2.4Ghz. I have used my Unix box and had a scan. So if anything, I would have thought the Extreme would be gearing more towards 5Ghz than not for my MBP as a less noisy option.

To add to my testing, I have introduced my old AirPort Express into the network. I have connected it to be able to use wireless speakers in iTunes. I have specified only the 5Ghz SSID to connect to and given it the WPA2 per shared key. Since the APX has been connected, my MBP hasn't switched over to 2.4Ghz once, despite connecting the iPhone, Xbox etc.

I wonder if this has anything at all to do with it? Also, I am now wondering if the Extreme has a bit of "settling in" time? Unlikely but you never know.

I'll give it a few days, try with and without the APX connected, connect my Xbox, iPhone, etc... and see what happens and report back.

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Answer 5

Mar 20, 2011 12:01 PM in response to Matt NewBones

I would have thought the Extreme would be gearing more towards 5Ghz than not for my MBP as a less noisy option.

The Extreme or any other dual band router does not "gear" towards anything. It simply broadcasts the two 2.4 GHZ and 5 GHz signals so that computers can decide how to connect.

It's up to the computer to make a judgment about signal quality based on a complex formula that takes a number of things into account. Which frequency, how strong is the signal, how does the noise look, etc?. That's all built into the operating system of the computer. We have no control over this.

If you are using the AirPort Express to "extend" 5 GHZ, then you have a much stronger signal overall. That additional signal may be allowing the computer to decide to stay connected to 5 GHz.

Keep in mind that if you are using the default 5 GHz settings, and you look closely, you'll see that the signal is 802.11a/n 5 GHz. "a" only operates at 54 Mpbs, the same as "g" on 2.4 GHz. Maybe you are seeing the computer connect to the "a" component of the 5 GHz signal?

Do you want to make the signal +802.11n only+ 5 GHz?

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Answer 6

Mar 20, 2011 12:33 PM in response to Bob Timmons

That's right, it's doing just that, extending the network. I hope I don't have to rely on turning the Express on to ensure 5Ghz n connectivity.

+Keep in mind that if you are using the default 5 GHz settings, and you look closely, you'll see that the signal is 802.11a/n 5 GHz. "a" only operates at 54 Mpbs, the same as "g" on 2.4 GHz. Maybe you are seeing the computer connect to the "a" component of the 5 GHz signal?+

The reason I renamed the 5Ghz network was so I could easily see if I am connected to my 5Ghz or 2.4Ghz broadcast. If I Option click my Airport icon, my PHY mode is consistently 802.11n.

Hopefully a firmware update will allow more restrictive control over the two bands.

Do you think there is a tweak I can make on my MBP to lock it to 5Ghz n?
Yes, I want to make the 5Ghz signal 802.11n only and have the 2.4Ghz g available for other devices.

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Answer 7

Mar 20, 2011 12:50 PM in response to Matt NewBones

Do you think there is a tweak I can make on my MBP to lock it to 5Ghz n?

No, all you can do is tell the MBP to connect to the 5 GHz network first in the connection order settings.

Yes, I want to make the 5Ghz signal 802.11n only and have the 2.4Ghz g available for other devices.

Open AirPort Utility - Click Manual Setup
Click the Wireless tab
Hold down the option key on your Mac while you click on the Radio Mode settings box and you may be surprised to find a number of choices that you may not have known even existed.

You would probably want to choose one of the following modes:

802.11n only (5 GHZ) -- 802.11b/g/n

802.11n only (5 GHz) -- 802.11b/g

The dashes separate the 5 GHz mode on the left from the 2.4 GHz mode on the right.
If you keep the default 802.11a/n setting for 5 GHZ, you give your computer an option to connect at "a" wireless speeds of only 54 Mbps, same as "g" wireless.

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Answer 8

Mar 20, 2011 1:11 PM in response to Bob Timmons

Thanks, yes, I had looked through all of these options this morning, I suppose what I'm looking for is to be able to set one SSID to 5Ghz n only and one SSID to 2.4Ghz b/g.

I'll see how it goes over the next few days and hopefully it will behave like yours, where the switching doesn't happen.

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Answer 9

Mar 20, 2011 1:12 PM in response to Matt NewBones

...and have them independent of the switching possibility...

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Answer 10

Mar 23, 2011 2:35 PM in response to Bob Timmons

All is well with the AirPort Extreme. If I make a change e.g. add a MAC address to my ACL and save meaning a reboot of the device, then I am switched over to the 2.4Ghz broadcast. Other than that, my MacBook Pro stays on the 5Ghz network so I'm happy.

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