Wireless Access

We are running ArubaOS 6.1.3.0 on M3 controllers with 11a band-steering turned on.

 

The issue is that the signal strength on our guest wireless (with the captive portal) is stronger than our secure wireless running WPA2.  The user experience is, of course, more bars.  I usually don't have any metrics to go on and it is usually reported so after the fact that even Airwave doesn't help me hone in on the AP on which they were associated.  One report late last week provided a screenshot of the open WLAN with full bars and the WPA2 WLAN was so poort it wasn't even listed in the list.  Both of these WLANs are in all of my AP groups.

 

I can think of a couple of reasons.  But, I am not sure if they are valid.  Could the open WLAN be seen on the bg radio and the WPA2 WLAN be seen on the a radio?  However, as I look at my BSS table, I can see that the bg radio has a lower EIRP/max-EIRP than the a radio.  So, that wouldn't make sense.  I do have spectrum load balancing turned on.  So, I guess the client could be using a different AP for the two WLANs.  Is this possible?  Unless the client is super close to an AP and the signal strength is just superb on both networks, then you almost always see a difference.  Is this due to overhead of the WPA2 encryption versus no encryption on the open network?

 

Thanks!

jcrouch, 

 

Enabling band-steering does not mean that the SSID will be seen only on the a-band. 

 

Controller maintains a list of clients capable of associating on 5GHz. When the AP receives a probe-request from the client on 2.4 GHz, the AP checks to see if the client is present in the list of 5GHz capable clients. If yes, then the AP will not send a probe-response on 2.4GHz and wait for the client to send probe response on 5GHz. 

For persistent clients, i.e. clients who keep sending probe-request on 2.4 GHz, the AP will send a probe-response in 8-10 seconds on 2.4GHz and allow the client to associate on 2.4GHz. 

 

It would be best to get a wireless utility on the client that can show the BSSIDs and their signal level and then compare the signal strength of the two SSIDs from the same AP. 

 

 

 

Download inSSIDer from MeteGeek. Best free program for this. No, encryption should not have anything to do with signal strength. Check both ssid profiles under advanced an see if the data rates are different. Screen shots will help us hel you :-)

Here are some screenshots to look at.  ONe of them shows LSUHealth-Public-Wifi in the list, but no LSUHSCS (the WPA2-ENT WLAN).  Both of these networks are in every single AP group on the controllers.  Another screenshot shows that LSUHSCS is back, but only after manually adding the network profile.  You can see a lower signal strength.  The two other screenshots show the data rates are the same for both VAPs.

 

I am going to look at the inSSIDer and check this out.

 

Jcrouch,

 

Is the LSUHSCS wlan hidden?

You also should check things like "local probe request threshold" and which rates are enabled (both under advanced SSID profile settings).  Those may change how SSIDs are seen in the air.

I just saw the images you sent and obviuosly the rates are not changed, so thats not the problem.  What about the probe request threshold parameter?

@cjoseph

 

LSUHSCS is not hidden.

 

@olino

 

local probe request threshold is disabled (set to 0).  I had been toying with the idea of setting this to something.  But, 1) I do not know what would be recommended, 2) I don't want to break a production network that is working for the majority of users and 3) I was sort of waiting for additional deployments that are underway to get our facilty much closer to 100% or more coverage.  Thoughts?

jcrouch,

 

What type of access points are these?

The Windows Supplicant does not mention which access point it is reporting when it reports signal strength.  It also does not always report the strongest one or the same access point for all WLANs it monitors.  With that being said, try to use a utility like inssider to see the true signal strength of access points and the WLANs they are broadcasting for a more fair comparison.

 

 

Thanks @cjoseph.  I very much like inssider.  Unfortunately, since downloading it, I haven't been able to troubleshoot this problem as the stakeholder has been out of the country.  But, I will keep inssider in my bag of tricks.

@cjoseph.  Related to this, would you recommend using local probe request threshold?  As I understand it, it prevents clients from receibing a probe response from the AP if the signal quality is too low.  If you do recommend this, what would you set this threshold to on a conservative level and on an agressive level?  I would like to start conservatively.  But, in case I need to get aggressive, I would like to know what is recommended to work my way up to.  I understand that if you set it to high then no one will be able to connect.

 

Also, if I enable this, is it just a matter of setting the threshold or do I need to enable something else?  I am running ArubaOS 6.1.3.0.

 

Thanks!

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@jcrouch wrote:

@cjoseph.  Related to this, would you recommend using local probe request threshold?  As I understand it, it prevents clients from receibing a probe response from the AP if the signal quality is too low.  If you do recommend this, what would you set this threshold to on a conservative level and on an agressive level?  I would like to start conservatively.  But, in case I need to get aggressive, I would like to know what is recommended to work my way up to.  I understand that if you set it to high then no one will be able to connect.

 

Also, if I enable this, is it just a matter of setting the threshold or do I need to enable something else?  I am running ArubaOS 6.1.3.0.

 

Thanks!

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jcrouch,

 

First, you have to determine if the access point is indeed broadcasting significantly different signal strength.  This will occur because the 2.4ghz spectrum propagates better than the 5ghz spectrum in certain circumstances.  If you do not have that problem you would not need to use the local probe response threshold parameter.

 

If you do choose to use the local probe respondse threshold parameter, 30 is a good number to start off with.  Anything higher, like 35 is more aggressive.

 

Just like any parameter that you change from the default, you must monitor your client behavior so make sure that you are not adversely affecting clients, because they do not all respond uniformly to such changes.

 

I have installed InSSIDer please guide what signal range is minimum, Average and Maximum Signal level should be maintained inside the covering area of WLAN

The range is arbitrary.  We want to just make sure that the signal strength on two SSIDs on the same AP are similar.

 

Reference to this case You are right. But for the sake of general knowledge i want to know what Signal strength is good for WLAN

It is all relative.  Connect to an access point in your environment where you are getting good performance.  Measure the signal strength.  That will be your good signal.

 

Quite a few things affect signal strength and you need to baseline your environment to see what is good for you.

 

Thank Joseph,

 

You are so kind and helping, Infact You are my Wireless Techonology Teacher Now :-)