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Wondering if anyone can give me some guidance here. I'm looking to create an optimized network for 5GHz N users primarily but with access to 2.4GHz for guests when they show up. I have an Airport Extreme (100Mbps Ethernet) and an Airport Express (B/G) that I would like to bridge together. The Airport Extreme would be in 5GHz mode only and the Express would be in 2.4GHz mode and they both have access to wired Ethernet.

I was thinking I could create a WiFi mesh by plugging the Airport Express in to one of the LAN ports on the Extreme but it seems that to extend the network Apple really wants me to use Wireless. The problem with this is that as soon as I enable WDS mode the Extreme base station goes back to 2.4GHz which I don't want.

Is there a way to link the Airport Extreme and keep it in 5GHz mode only and add an Airport Express and have it host the same wireless network? In addition, is there a way to force the clients to join the 5GHz network by default if they can and fail back to the 2.4GHz network?

My last option is to simply change the Airport mode any time a guest with a B/G network card comes over, but fundamentally I'm too lazy to do that all the time and would love it if my network just had both wireless options optimized.

Thanks,

B

You don't need WDS to do what you want.

You can plug the Express into one of the Extreme's LAN ports and have both host different wireless networks. Set up the Extreme as a pure 5 GHz 802.11n device and the Express as a 2.4 GHz 802.11g device in bridge mode.

The key is to setup a "dual-band network" according to Apple's simple guide (page 48).


In your case you just put your Extreme where Apple has put TC and you set up your Express where Apple has put the Extreme. Give the networks different names so you can distinguish them. Set up your n devices to connect to the n network automatically.

I do exactly this, and it works excellent. Faster speed for n-computers with b/g available for older computers and iPhones.

Keep in mind that "n" uses both frequency ranges, so by limiting your n devices to the 5GHz band will potentially slow them down. On the other hand, having a b/g network co-exist will cause more lag on the lower frequency range (as broadcasts/collisions etc. will run at the lower speed of the frequency, while still polluting the n transport).

Good wireless network design still requires more than the simple Apple guide, although as I contributed to that I can't get too bitchy.

802.11n does not simultaneously run on 2.4 and 5ghz. A client will use only one range at a time, and most routers do the same. The few routers that do support having both frequencies active still create 2 discrete networks. n can use multiple channels in the same frequency range to increase speed.

And as the others described, create two wireless networks. I have my Buffalo router set to create "Network Sector Five" in the 5ghz range and n only, then "Network Sector Two" as a 2.4ghz b/g only network. Also for extra coverage, I have an Airport Express (older g model) wired into the network and set to also create "Network Sector Two" with the same wireless key, but on a different channel. b/g clients automatically pick the one with the best signal.

Ditto.

802.11n does not simultaneously run on 2.4 and 5ghz.
Which draft standard are you speaking of?
A client will use only one range at a time, and most routers do the same. The few routers that do support having both frequencies active still create 2 discrete networks. n can use multiple channels in the same frequency range to increase speed.
Actually, not so: you can tell the router to use separate SSID's for each frequency range, but you effectively limit the flexibility available to the network. Using one SSID for both is (currently) the most logical and forward thinking route to take.

Try Wikipedia as a good starting point.

Unless of course you want your n devices to stay in a frequency range that is less crowded and less noisy.

I really don't understand what you're arguing here. There have been several benchmarks done with Macs and the AEBS that show an n capable Mac will usually get better wireless performance if it is running on a pure 5 GHz n network. If somebody has an extra BS lying around, why not split up and let the n devices get better performance? You're losing nothing by doing so.

And you can do all that with one SSID, you don't need two. The SSID is analogous to the old AppleTalk zone names: it exists for users, but (just as having Zone X appear on EtherTalk and LocalTalk) it has nothing whatsoever to do with performance, which is a network function, not a UI one.

Are you saying that an AirPort card differentiates by both SSID and frequency band? Most wireless cards (all that I know of-unless there's something special about AirPort cards) key on the SSID-if they find it, they connect to it. This is how ESSIDs work in roaming networks. All the access points use the same SSID, but they're all on different channels, so the client card sees the right name, then uses a search algorithm to find where in the DSSS pattern on the detected channel that particular access point is. As the user moves and the signal strength changes, the card can switch from one access point to another with a stronger signal.

Having the same SSID on two different bands can cause some "interesting" behavior because of this.

Yes, you have it in a nutshell. If I have an SSID of "whatever" on b/g and another on "a" (there is no "n" bandwidth, as I'm sure you know) the client will bind/connect to the "best" access point (b/g or a): if it can get a good 2.4MHz signal, it will use that if it can't get a good 5Mhz signal. And if you move around, it will switch between whatever AP works "best". This is part of the 802.11g specification (to move between 'g' speeds and 'b' speeds as required) - extended to work with 'n'.

An 802.11n setup will simply use as many channels as it can in both the 'a' range and the 'b/g' range.

Sweet huh?

And yet my n capable Macs get higher speeds if the AEBS is set to pure 5 GHz n rather than 2.4/5GHz mixed g/n.

These theories are all nice, but in the end whatever's faster and more reliable wins for me.

You're saying basically the same thing I am-that having the same SSID means that the client will move to whichever one has the best signal. That's just a setup I'd never considered because of the scarcity of (and in the past lack of desirability of) multi-protocol networks. Have you looked for an A router or access point lately? They're not common and none are in the "consumer" price range as far as I'm concerned. But N hardware is changing that.

There are some issues to consider on this though-for example, you MUST have all of these access points/routers on the same network and with the same Internet connection, or when you change from one to another you could lose whatever you're downloading. That usually means having the same routing path, so it can get tricky, especially if you have multiple access points/routers right next to each other-even if they're on different bands, the radiated power of one can interfere with all the others. Best to have them physically separated. In a true roaming environment they'd be spread out for coverage and this wouldn't be a problem.

In the diagram shown in the second post, shouldn't the ethernet cable connecting the Airport Extreme and the Time Capsule be connected to the WAN port on the Airport Extreme and not the LAN port as pictured?

Yes. You run an Ethernet cable from one of the TC LAN ports to the AEBS's WAN port and set the AEBS to bridge mode.