Two Networks Same Building

Unanswered Question
Nov 21st, 2008

We own a multi story building and have operations on two floors. On Floor 10 I have autonomous 1210 APs with ssid ZNDWireless running LEAP authentication with WDS. On Floor 4 I have deployed LWAPP 1242s with a WLC-4404 4.2.130 using the same ssid ZNDWireless with LEAP to same Radius/CiscoSecureACS 4.1. Between Autonomous and LWAP the SSIDs are on same vlans, etc. The goal was to be able to go between 10th and 4th floor and not care if you are on LWAPP or Autonomous APs.

I noticed sometimes the 4th Symbol PPT8800 clients associate to the 10th floor APs and have poor connectivity, etc. I was standing under a 4th floor AP with a Symbol today when the symbol associated to the 10th floor much to my suprise.

The 10th floor power on autonomous AP is set to 50mw, while the 4th floor WLC/WCS set the power level to 2 (12.5mw).

In short I'm thinking all our APs need to be either autonomous or LWAP, not a mixture in same building.

I have this problem too.
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jeff.kish Fri, 11/21/2008 - 14:19

Actually, this has nothing to do with autonomous vs lightweight. This sounds like a physical layer issue. Somehow you have extremely thin floors and the signal from your 50mW APs is leaking and overpowering your 12.5mW APs.

Sadly, roaming is determined solely by the client, which means that there's not much you can do to prevent your APs from roaming to undesired APs. About the only thing you can do is set MAC authentication on the APs, but that's a nightmare to manage unless you're only talking 10 or less clients.

Converting your 10th floor APs to LWAPP will improve roaming efficiency, but the problem is that you don't want them to roam at all. What kinds of antennas are you using? I'm shocked that the signal manages to make it through 6 floors and still be sufficiently strong to allow a roam.

Ultimately, I'd tweak power levels. Try decreasing your 10th Floor APs and increasing your 4th floor APs. But I gotta say that I don't think upgrading to LWAPP on the 10th floor will fix this particular issue, though it will certainly offer many other improvements.

If the imporvements of LWAPP are worth it then I would upgrade.

Lowering the power on the 10th floor AP's enough to get them not to even show up on the 4th floor would be my first step.

Increasing the power on the 4th floor AP's as needed to ensure full floor coverage would be the second step. Making sure not to reverse my problem by having 4th floor AP's show up on 10.

I am somewhat shocked as well that the 50mw 10th floor is showing up on 4. I would also be surprised as you are about it joining the 10th floor ap while standing under the 4th floor ap. However Jeff is right roaming is up the client and I'm betting the client saw a higher signal from the 10th floor. Which points to transmit power.

dziminski Tue, 12/02/2008 - 13:54

I ran into an issue where the Intel 5300 wifi card could not connect to APs on certain controllers. Basically this gave me the same problem. Laptops would connect to APs on a different floor with an extremely poor signal.

After many hours of troubleshooting and wireless sniffer captures, I saw that the beacons and probe responses were slightly different on APs on certain controllers. The Intel card didn't like the beacon and refused to associate. The bad APs were missing a "unicast cipher suite" in the RSN Information section of the beacon. This didn't bother other wireless clients, but the Intel card didn't like it.

The configs were identical on the controllers. Removing and re-adding the SSID fixed the issue. Now all APs have the unicast cipher suite in the beacon. This is clearly a bug.

I recommend you perform wireless packet captures and closely compare the beacons and the association process to see why the laptops are not connecting to the closest AP.


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