Cisco Wireless Help

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staticz

Limp Gawd
Joined
Feb 19, 2008
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We have approximately 150 1142 LWAPP's deployed in our facility. Recently we started getting complaints about speed issues (90% are using G 10% N). Upon investigating we found that the speeds are flucuating rapidly. Everything from 54Mbps down to 1Mbps and back up again. I've confirmed that this will happen while standing next to an AP (and confirming connectivity to it), however I cannot find anything wrong or anything that has changed with our configuration. We are a large facility and it is happening all over the campus, so I'm fairly certain it isn't any type of 'normal' interferance.

I've checked for channel issues and everything seems to be managing itself properly, I just can't figure out what the issue is. Any help would be greatly appreciated!

edit: We peak around 700-800 clients at any one time, though I've seen the issue occur on an AP that only has 5 connections.
 
Anything in your enterprise that also operates at 2.4Ghz that might be causing interference?
Is your N operating at 5ghz? If so, turn off the G radios from the AP's for a few hours and have your N clients test things and see if the problem remains.
 
Nothing else runs on 2.4

We have over 700 users (re: employees) on wireless at any point, I cannot simply shut off the G radios. To add a bit more information it is happening on both Intel and Athereos chipsets, so I think that rules out a driver issue...
 
staticz said:
Nothing else runs on 2.4

We have over 700 users (re: employees) on wireless at any point, I cannot simply shut off the G radios. To add a bit more information it is happening on both Intel and Athereos chipsets, so I think that rules out a driver issue...
Click to expand...
I didn't say turn off during production.
Wait for a maintenance window. If this just started happening recently then something has changed. Some part of your environment is now different.
If your N clients (assuming they are 5ghz) have no problems it could be interference.
Also, you didn't mention if these are autonomous or lightweight.
Check if the WLC logs. Maybe even open a cisco TAC.
 
They are LWAPP like I said when I listed the model number. Been running on the same code set for over a year with no issues. At first we assumed it was client density so we added APs, but there was no change. If there was an interference issue that affected 3 blocks worth of buildings I think everyone would have cancer already :)

Cisco TAC says there are no issues with the controller, client load or APs and blame the client. I've gone through every channel but the forums!
 
Have you checked to make sure your APs are not interfering with each other? What is the SNR when you are standing in a spot testing?
 
I'll check that out and report back tomorrow, thanks for the suggestion.

WCS does not report any interference issues, not sure if it will pick up that type of interference though.
 
Are you using automatic channel & power selection? What channels are you allowing?

I assume if the speeds are fluctuating between 1-54mb this is only on G clients?
 
Yes, we're using auto-channeling and power. Yes to your second question as well, 90% of the clients are G clients.
 
Check if there is an exclusion option to only limit G to channels 1, 6, & 11. Also, I generally decrease the maximum power to 75% or less. I suggest these as a starting point to help mitigate channel overlap and interference.

I'd give you more details on how but its been a few years since i touched a cisco controller and i truthfully don't remember.
 
I had this problem, turned out my AP's were too close to each other and the controller was set to automatically manage which AP the clients are on. I turned that off and everything went to work fine. Also, I disable wireless B at all of my sites right off the bat.
 
Here is some data I picked up with inSSIDer:

F56OQ.png


I was unable to recreate the issue today but could the channel congestion be the problem? How can I eliminate that (decrease power?)?


thrash408 said:
I had this problem, turned out my AP's were too close to each other and the controller was set to automatically manage which AP the clients are on. I turned that off and everything went to work fine. Also, I disable wireless B at all of my sites right off the bat.
Click to expand...

Do you know what that parameter is called? Is it Client Load Balancing?
 
You are seeing wwwwwaaayyyy to many APs at once.

Do you have RRM turned on to manage the power level of the APs?

Also like previously mentioned disable B rates if you can.
 
klank said:
You are seeing wwwwwaaayyyy to many APs at once.

Do you have RRM turned on to manage the power level of the APs?

Also like previously mentioned disable B rates if you can.
Click to expand...

RRM is on and is supposed to be actively managing power levels and channeling. I'll disable the B rates on Monday (no changes are allowed on Fridays). Should i attempt to turn down the power manually?
 
I would leave the power levels alone until you can disable B rates. Don't want to change too many things too fast on a large network like yours.

Just one B client will drop an AP and ANY surrounding APs within RF earshot to B rates.
 
klank said:
I would leave the power levels alone until you can disable B rates. Don't want to change too many things too fast on a large network like yours.

Just one B client will drop an AP and ANY surrounding APs within RF earshot to B rates.
Click to expand...

*facepalm*

I have absolutely no idea why I didn't think of this. I will try it first thing Monday.
 
You really should be making these changes now or over the weekend.

Trying something first thing Monday is a terrible, terrible, terrible combination of words.

You should also eventually decrease the TX power and at least do manual channel selections in high-density zones.
 
Back to square one. I ran a few reports this morning and found out that there are 200 devices that are B only on the wireless network. They are split off onto their own SSID and have bene on the wireless network for years, ruling out this issue.

I'm beginning to wonder if I turn down the power manually if the problems will resolve. Is there any other info I can give you guys to help? Thanks for all of the input so far.
 
They can be on their own SSID but if that SSID is being broadcasted on the same radio as the other SSID's, B is still going to be the issue. Are your B clients on a separate wireless or on a separate AP grouping?
 
Are you filtering broadcast traffic on the wlan's? Broadcast traffic can absolutely kill your available bandwidth
 
Didn't want to leave this thread hanging in case anyone comes across it later. Working with Cisco we did exactly what some other folks had suggested - disabled all but one (11 mbps) B speeds.

We immediately saw channel utilization drop from 60%+ to <25% and we've confirmed stability in limited testing. Some other things Cisco recommended that might help others -

- Less than 10 SSIDs (we had 12)
- Hang a couple of APs and put them in monitor mode. The APs will report and make the controller more intelligent
- Even in a dense client area, APs should have a power level of at least 3, otherwise you're not getting much out of them. Solution to this - put APs in monitor mode or take them out.
 
Very cool, I do a lot with cisco wireless and i've never actually put any in maintenance mode. Did they send you any documentation on best practices on this? Glad you got it fixed, I learned the hard way about 11b as well when i first started in cisco wireless :p
 
thrash408 said:
Very cool, I do a lot with cisco wireless and i've never actually put any in maintenance mode. Did they send you any documentation on best practices on this? Glad you got it fixed, I learned the hard way about 11b as well when i first started in cisco wireless :p
Click to expand...

Nothing in regards to documentation. Just that when you turn one on it will knock anyone off who was on it. My understanding is that it helps the controller make better decisions in regards to power, channeling, etc.
 
Someone out there still uses wireless B?

Wow....


I've come across wireless G devices that did not have a WPA option, but a driver update fixed that.


What kind of devices don't have wireless G and aren't 10 years old? I'm racking my brain to think of any...
 
Mackintire said:
Someone out there still uses wireless B?

Wow....


I've come across wireless G devices that did not have a WPA option, but a driver update fixed that.


What kind of devices don't have wireless G and aren't 10 years old? I'm racking my brain to think of any...
Click to expand...

There is a ton of "B" out there still. You wouldn't believe how bad it is at sports stadiums.

Most of them are hand held scanners.
 
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