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Wireless clients bouncing up and down

tcasartello
Level 1
Level 1

We have a Cisco Unified wireless network on our college campus. There's an area of one of our dormitories where people are having an issue where they keep disassociating and reassociating to our wireless network. We have pretty dense coverage in that area (generally get about 5 bars,) and I haven't seen the issue in other areas on our campus. Anything in the area I should look for that could be causing that problem, or could it be a problem with out setup.

42 Replies 42

tcasartello
Level 1
Level 1

Just trying to see what kind of problem would cause bouncing on and off.

George Stefanick
VIP Alumni
VIP Alumni

Hello,

A few things an cause clients to bounce on and off a wireless network.

- Interference is a likely cause of a client to get bounced. Do you have a spectrum card that you can take readings?

- Malfunctioning Clients - I am assuming your client base is a wide mix based on you mentioning that you are a college campus. Is there anything in common with the clients that are getting bounced.

- Is the controller that is handling the access points for this building in the other controller domains?

- Is there a pattern to the disconnects. Does it happen around the same time each day?

"Satisfaction does not come from knowing the solution, it comes from knowing why." - Rosalind Franklin
___________________________________________________________

Leo Laohoo
Hall of Fame
Hall of Fame

I'd like to find out what the controllers' error logs.

What are the error messages reported from the clients' side?

Do the clients get Authenticated at all?

Every client I've tried over there will do it. Even my own laptop. I did notice this error in that area: Decrypt error occurred for client '00:22:5f:0a:a8:0c' using 'Unknown' key on '802.11b/g' interface of AP 'newdorm-b2-3-4'. This error comes up constantly. We're using an open network in that area so I don't know why I'd getting decrypt errors. All the APs in that whole building are on the same controller, with the same SSID, same mobility group, etc. There IS an AP on the outside of the building in a different mobility group but it has different ssids broadcasting. We do have a "secret" WPA2 802.1x ssid that doesn't broadcast, but no one knows about that but us IT folks.

What about the possibility there are too many APs to choose from, causing association thrashing? Try turning down the power and/or upping the minimum (Basic) data rate. Are the clients a/b/g? They could also be flapping between radios. Try fixing them to a single spectrum to see if they stabilize at all. I'd also disable all active (deauth-causing) Security Policy features.

I'm going to try disabling the A band and upping hte basic data rate. This is of course the one building I don't have heat maps in my WCS (due to lack of floor plans, going to try to aggressively push for our facilities department to give us some) for so it makes it much more difficult to troubleshoot.

I did the following which seems to have fixed the association bouncing:

- Disabled the A band on all APs

- Set minimum data rate to 11 MBPs.

- Checked off "Avoid Cisco AP Load"

I want to try to figure out which of these acutally fixed my problem. Any thoughts?

Still having major issues with this. Clients are essentially bouncing between various access points and its literally happening every few seconds to 5 minutes. While the earlier steps I took improved the situation for some people, it's still occuring in other places. I never had this problem last year. Over the summer we upgraded to version 6.0 of software on all our controllers. So I don't know why this is occuring now. Is there any other settings I could try?

Leo Laohoo
Hall of Fame
Hall of Fame

I would like to apologize for not reading your issue properly.

So you are saying the clients in a specific building is experiencing bouncing from one AP to another?

I was once doing a site survey and when I turn around a particular corner of the floor (where the AP is), my Airmagnet would crash and send the OS into the ubiquitous BSoD. After trying on another laptop with the same result, we decided to check the machinery room upstairs (directly above the AP) and we concluded that some kind of electrical interference is causing some kind of "jam" effect.

This dorminotry in question, do they have some kind of legacy-type machineries (mechanical and/or electrical)? Is this affecting the entire dormitory or just a few of the floors?

No the one where it's happening the most is actually our newest dorm what was built in 2004.

What do the RF measurements look like? They must be thrashing for a reason. I take it this code is in use elsewhere where there's no such phenomena?

Co-channel? Can you turn off the BG and see how only A clients behave?

Multipath? Try putting an 1142 in there.

Do you have Cognio (Cisco Spectrum Expert)? Probably a good idea to have anyway.

Leo Laohoo
Hall of Fame
Hall of Fame

Is this affecting the entire dormitory (built in 2004) or just a few of the floors?

ED CARMODY
Level 4
Level 4

Get somebody out there with a wireless packet sniffer and a spectrum analyzer... you'll know in 10 minutes what's going on... smells like interference or a bad AP to me.

TAC lended us a cognio specturm card. We also did some wireless sniffer capture and they did not see any deauth packets or anything like that. As far as the cognio spectrum card, they said they are seeing some type of interference across all the channels and some strange devices showing up. We're going to try to look into that. The one thing that's weirdest about this, is that when I reboot all the access points, it stablizes all the clients for about a week or so, then the problems start slowly creeping back again.

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