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Further to an earlier mail, I have done some reaearch on site into a problem where the clients drop off the network. See what you think:

1) 2.4 GHz spectrum analysis shows no rogue interference.
2) Monitoring the signal with Inssider and Airmagnet shows the AP signal suddenly dropping every once in a while.
3) Capture shows the client issue a disassociation then a reassociation.
4) The signal comes back up quickly so the client reassociates with the same access point.
5) Vist, XP, doesn't matter, all clients in the area re-associate.

For the user, what they see is that every so often they lose connection, then it comes back.

The access points are Cisco 1240, no controller, single SSID. I have good 1,6,11 spacing and no signal overriding the nearest access points. I surveyed with Ekahau and everything seems fine.

So, what on earth can I do to stop this from happening ?

I am pretty stumped...

Any answers greatly appreciated.

-Neil Mac

what version of firmware are you running on the Cisco AP? we had some random drop off a while back similar to what you describe and it was firmware

12.3(8)JEA

Normally stable...

Funny though, I have these access points with this release in other places and they are fine, I am pretty stumped as to what the cause is.

I will upgrade and see how it goes.

Please if anyone else has an idea, let me know.

-Neil

Question 1: You say the signal drops off, does the RSSI drop substantially or go away entirely?

Question 2: Does this observation of falling RSSI happen only in certain areas per previous post or can it happen with all 22 AP?¡é?€??s?

Question 3: Are radio 1?¡é?€??s disabled?

Question 4: What solution are you implementing to power the AP?¡é?€??s?

Question 5: Did you change the network, 6 SSID?¡é?€??s to 1, controller to no controller, to simplify trouble-shooting?

Question 1: You say the signal drops off, does the RSSI drop substantially or go away entirely?

Question 2: Does this observation of falling RSSI happen only in certain areas per previous post or can it happen with all 22 AP?¡é?€??s?

Question 3: Are radio 1?¡é?€??s disabled?

Question 4: What solution are you implementing to power the AP?¡é?€??s?

Question 5: Did you change the network, 6 SSID?¡é?€??s to 1, controller to no controller, to simplify trouble-shooting?

OK, good questions, here are the answers:

1: The signal drops to virtually nothing, measured on 2 different pc's, one with inssider, the other with AirMagnet.


2: This happens in two areas, but due to the nature of the site, they are the only two areas where people are - I didn't get a chance to test fully in other areas. However, it's pretty consistent.

3- Yep, just the b/g enabled, though I am going to fit antennas and turn on the a radios.

4. They are POE from Linksys switches.

5: We don't have a controller, there are 6 access points and 3 repeaters.


I discussed the firmware with a Cisco guru, he reckons the firmware is very stable, I haven't changed it yet.

I made a second ekahau survey and I do see some interference from the yard access points - (The installation ison a boat which is currently in a yard.)). However, this problem began when the boat was at sea, according to the crew.

Neil

What did you use to perform the spectrum analysis?

Is it an AP that is failing or a repeater? If they are AP's that are failing, do they have repeaters attached?

Gene

Hi Gene.

I used WiSpy 3.1.

The failing WiFi's are not associated with the repeaters.

Neil

Is it possible that you could send me a packet capture of the drop off occurring? I'm not sure what you are using for packet capture, but if you have it in native Omnipeek that would be great. Shoot me a PM if you like and I'll send you my email address.

If Wi-Spy isn't showing any interference then we have to assume either the AP's aren't acting correctly or the STA's aren't playing nice. Since you have tried two different STA's, then it begins to point to the AP's. A packet capture should help.

Gene

Hi, Gene.

I didn't save the capture unfortunately, it was pretty clear what was there and I can tell you what I saw.

As the signal dropped, the STA issues a disassociation frame, then a reassociation frame, which reassociated back to the same AP as the signal was back.

So it was kind of roaming, but to the same AP.

I have a guy going back to the site tomorrow, and will chack a couple of things. I have suspicions about interference from the yard AP's, though this happens (apparantly) in open sea also.

So I will see what we can do to confirm either way.

Neil