07-19-13 Expert Day

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New Contributor

Roaming/connection issues for wireless clients

Hello, in our environment (2000+ AP's) we have situations where clients on some days, typically on a MAC, constantly roam from AP to AP in what seems like 10 min intervals, and in the process lose their connection.  What are some good troubleshooting techniques to isolate the cause of the client dropping their connection?  Correct me if I'm wrong, but shouldn't these roaming events be invisible to the client?  

 

Also, at times a client can be directly under an AP, but instead connect to an AP a few floors up or way down the hall, can someone explain this behavior?  What is it exactly that may make an AP, with what should be a much stronger signal, unavailable to a client for connection?  We've run a spectrum analysis at the location and didn't detect any sources of interference, but it could of just been a timing issue.

Occasional Contributor II

Re: Roaming/connection issues for wireless clients

some of this can be contributed directly to client drivers and others may be a symptom of some other issue

 

does the MAC have an Atheros chipset? Which model?

 

Also, what is your arm scan intervals set to?  Do ap power shifts coincide with your user roaming issue?

 

Is band steering or spectrum load balancing enabled?

-Brian

Network Engineering|Texas A&M University
pacecar02@exchange.tamu.edu
Aruba Employee

Re: Roaming/connection issues for wireless clients

Also, do you have Client Aware enabled? Sometimes a channel change during the day might cause a client to roam off of an AP and onto another one.

 

As for losing connectivity while roaming, if your device has a different IP after roaming, you will see that symptom. Are you using VLAN Pooling, if so, what is the hashing algorith that you are using? Are you sharing all your user VLANs across all the controllers?

ACE Engineer
ACMX, ACDX, CISSP, B. Eng.
New Contributor

Re: Roaming/connection issues for wireless clients

I just checked the ARM profile for the A and G radios on the AP in question and the scan interval (sec) is set to 10, so 10 seconds?  We just upgraded our controllers last week to 6.3 and now have active client match with band steering etc, but this was happening prior to the upgrade.  I'm just at a loss as to why the client has to lose their connection and have connectivity interrupted for ARM events, unless of course interference or utilization was so great that a roam was necessary.  Is it typical for clients to lose connection due to ARM events?

 

 

New Contributor

Re: Roaming/connection issues for wireless clients

@ guillaume, yes client aware is enabled.  Most times when this was happening to the client I checked the AP and radio's for channel changes and there were none.  On the client detail page under associations, it shows the user kept the same IP addr as she hopped from AP to AP during the day.  

 

We just implemented VLAN pooling this morning actually, so no at the time of these issues, VLAN pooling was not in place. 

 

I'm trying to get a better idea of how exactly to determine why the connection was dropped if all they are doing in essence is roaming to what the client or the AP believes is the preferred AP to connect to.  Is there a log, or certain command that can be run to get more detail as to what caused a connection drop?

Aruba Employee

Re: Roaming/connection issues for wireless clients

10 seconds is the default scan interval, which is fine and I suggest that you do not modify it.

 

A scan will not make a client lose connectivity, neither will a power change (unless the new value is now too low for the client). A channel change will require that the client reconnect so there might be a 'blip' in connectivity at that point.

 

I do not think the issue is related to ARM scanning or ARM events, but to other factors instead.

 

Can you give us a bit more information on your infrastructure? User VLANs and how is that setup? What are you min/max settings for power levels in ARM?

ACE Engineer
ACMX, ACDX, CISSP, B. Eng.
Occasional Contributor II

Re: Roaming/connection issues for wireless clients

Take a look at the arm history of the aps in question

Also go ahead and start debugging the client mac

The short answer is no the user session should not be interrupted for general arm events, but as guillaume mentioned is the user maintaining the same ip address throughout this roam?

-Brian

Network Engineering|Texas A&M University
pacecar02@exchange.tamu.edu
New Contributor

Re: Roaming/connection issues for wireless clients

@ guillaume - max/min power for G radio is 18/12 and for A it's 21/12.  As of this morning we implemented 40+ vlan pools size /23.

 

@ pacecar02 - can you provide the command to debug a client MAC?  Does enabling a debug performance degrading at all for the AP or controller?

On one occasion the user kept her IP during each roam, and another time I recall a user continually changing IP's during the roam, can you advise on what the IP addr changing with each roam may indicate?

Occasional Contributor II

Re: Roaming/connection issues for wireless clients

only leave logging debug user on while troubleshooting

 

not necessarily performance impacting but should not be left on

 

(config) #logging level debugging user-debug <mac>

 

edit: to see the log

 

#show log user-debug all or #show log user-debug all | inc <mac>

-Brian

Network Engineering|Texas A&M University
pacecar02@exchange.tamu.edu
Aruba Employee

Re: Roaming/connection issues for wireless clients

Hi dk2733,

 

Since clientmatch is enabled, i'd recommend the following debug as well,

 

To enable:

#logging level debugging arm -user-debug <client-mac>

 

To show the logs:

#show log arm-user-debug all

 

This will perform user-debug for client-match related events (i.e., now that you have upgraded to 6.3, some of the client association change might be triggered due to clientmatch being enabled).

Barath Srinivasan
Customer Engineering Architect
Customer Advocacy | Aruba Networks Inc.
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