5 GHz vs. 2.4 GHz WLANs

Answered Question
Dec 6th, 2011

I am preparing to set up guest wireless access in a dorm environment with a Cisco 5508 WLAN controller and Cisco 3602i APs.  According to the book I've been reading, it recommends that I set up a WLAN for 802.11a/n clients in the 5 GHz range and another WLAN for 802.11b/g clients in the 2.4 GHz range.  It recommends giving them an SSID like "Guest - 5GHz" and "Guest - 2.4 GHz" respectively.  Their reasoning is to allow the best experience for 802.11n users while still supporting legacy devices.  Is this a good idea, or should I simply set up a single WLAN for 802.11b/g/n on in the 2.4 GHz range until the 5GHz range has greater adoption? 

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Correct Answer by George Stefanick about 2 years 4 months ago

I have a different stance. I would allow guest with 802.11n speeds and here is why I state that. Wireless is a half duplex medium. If I can get a guest frame on and off the medium 5 times faster with 802.11n, why not. Other wise, your guest clients are the slow pokes on the high way that everyone is trying to get around ...

just my 2 pennys ..

Correct Answer by Scott Fella about 2 years 4 months ago

I would just use one SSID for guest. If you want guest to be on a different subnet than your management, then I would create a dynamic interface for guest and use that interface.

Sent from my iPhone

Correct Answer by Scott Fella about 2 years 4 months ago

I would just use one SSID, keeps the confusion level down. The only time I would restrict the guest wireless is if I have devices that utilize the 5ghz and that is when I would only allow guest on the 2.4ghz. Conserve my bandwidth per say. I have also disable 802.11N so the max a guest user could connect to is 54mbps, it really depends on your install and if its only guest that will be on your wireless.

Correct Answer by George Stefanick about 2 years 4 months ago

Hi Ryan,

For starters you can only bond on 5 ghz. What this means is that you will only get 300 meg on the 5 ghz side. On the 2.4 side you will get 144 at best, due to non bonding.

My stance is allow guest on both, so one 1 ssid. You wll get a mix of guest on 2.4 and 5 ghz. Unless there are compelling  reasons not to.

As for 5 Ghz and adoption, almost all new devices support 5 GHz and 802.11n. Dont be surprised if you see more guest on 5 GHz than 2.4.

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Correct Answer
Scott Fella Tue, 12/06/2011 - 12:35

I would just use one SSID, keeps the confusion level down. The only time I would restrict the guest wireless is if I have devices that utilize the 5ghz and that is when I would only allow guest on the 2.4ghz. Conserve my bandwidth per say. I have also disable 802.11N so the max a guest user could connect to is 54mbps, it really depends on your install and if its only guest that will be on your wireless.

SchurmanRyan Tue, 12/06/2011 - 12:47

So to clarify, use one guest SSID and just allow all radios?

A side question to go with it... do I need to keep the default WLAN that's mapped to the management interface that was created when I setup my controller?  I can't find any info about it...

Correct Answer
Scott Fella Tue, 12/06/2011 - 12:51

I would just use one SSID for guest. If you want guest to be on a different subnet than your management, then I would create a dynamic interface for guest and use that interface.

Sent from my iPhone

Correct Answer
George Stefanick Tue, 12/06/2011 - 12:57

I have a different stance. I would allow guest with 802.11n speeds and here is why I state that. Wireless is a half duplex medium. If I can get a guest frame on and off the medium 5 times faster with 802.11n, why not. Other wise, your guest clients are the slow pokes on the high way that everyone is trying to get around ...

just my 2 pennys ..

George Stefanick Tue, 12/06/2011 - 12:59

Ryan,

never use the managment vlan for any WLAN. Other wise clients will be sitting in the same VLAN as your managment intrerfaces to you WLCs.

As Scott pointed out. You should map your guest to a sperate VLAN that is either anchored to another WLC in the DMZ OR has ACLs blocking it from the network.

Also, make sure you apply proper QoS settings to your guest traffic so they dont take priority over your other traffic. If you give guest bronze status the NAC timers are longer for guest clients.

SchurmanRyan Wed, 12/07/2011 - 07:47

Thanks George.  If I had to allow older clients on the network, have you had any experience with using Client Band Select? 

Correct Answer
George Stefanick Tue, 12/06/2011 - 12:34

Hi Ryan,

For starters you can only bond on 5 ghz. What this means is that you will only get 300 meg on the 5 ghz side. On the 2.4 side you will get 144 at best, due to non bonding.

My stance is allow guest on both, so one 1 ssid. You wll get a mix of guest on 2.4 and 5 ghz. Unless there are compelling  reasons not to.

As for 5 Ghz and adoption, almost all new devices support 5 GHz and 802.11n. Dont be surprised if you see more guest on 5 GHz than 2.4.

Leo Laohoo Tue, 12/06/2011 - 13:23
For starters you can only bond on 5 ghz. What this means is that you will only get 300 meg on the 5 ghz side.

Sorry George, I'll disagree with you on this.

With 3602i, you get 4 x 4 MIMO.  This means that with channel bonding, you'll be seeing a potential 450 mbps of bandwidth.

George Stefanick Tue, 12/06/2011 - 13:35

I over looked the 3602i comment. Then YES, ... but the 4x4 wont get you 450, the 4 spatials will get you 450

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Posted December 6, 2011 at 12:25 PM
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