Question : Cisco WLAN - Roaming help.

Hey all!

I am working on my first implementation of a wireless LAN controller. Specifically the Cisco WLC2112. I am using 8 access point all of which are 1130s. I have set up two WLANs on separate VLANs and everyone is authenticating and connecting without issue.

What I am looking for help on is roaming. I need to understand better how roaming occurs first off. Is is initiated by the host or by the controller? I have a couple of devices that are a little "sticky", by that I mean they seem to just want to stay connected to one access point even if they are a lot closer to another one. It will often require the signal from the connected access point to get to almost nothing before it will connect to the closer AP.

I am new to WLAN controllers so I need a bit of knowledge as well as advice. Is there a way to have the WLC force a client to use a different AP on the fly? Or is this a host issue that cannot be addressed in the controller alone? How does a WLAN controller manage hosts as they move around the coverage area of multiple APs?

Last note: there is only one WLAN controller, I am not worried about roaming across controllers just APs.

Thanks in advance!

Answer : Cisco WLAN - Roaming help.

Well I did it using WLC 4402 but I assume there is a lot of similarity between theses controllers.

That is how you can set limits on WLC:

• log on to WLC 

• go to Wireless > 802.11a/n (or 802.11b/g/n) > Client Roaming 

• If you want to fine-tune the RF parameters that affect client roaming, choose Custom from the Mode drop-down box. 

• In the Minimum RSSI field, enter a value for the minimum received signal strength indicator (RSSI) required for the client to associate to an access point. If the client’s average received signal power dips below this threshold, reliable communication is usually impossible. Therefore, clients must already have found and roamed to another access point with a stronger signal before the minimum RSSI value is reached. Range: –80 to –90 dBm Default: –85 dBm 

• In the Hysteresis field, enter a value to indicate how much greater the signal strength of a neighboring access point must be in order for the client to roam to it. This parameter is intended to reduce the amount of roaming between access points if the client is physically located on or near the border between two access points. Range: 2 to 4 dB Default: 2 dB 

• - In the Scan Threshold field, enter the minimum RSSI that is allowed before the client should roam to a better access point. When the RSSI drops below the specified value, the client must be able to roam to a better access point within the specified transition time. This parameter also provides a power-save method to minimize the time that the client spends in active or passive scanning. For example, the client can scan slowly when the RSSI is above the threshold and scan more rapidly when below the threshold. Range: –70 to –77 dBm Default: –72 dBm 

• In the Transition Time field, enter the maximum time allowed for the client to detect a suitable neighboring access point to roam to and to complete the roam, whenever the RSSI from the client’s associated access point is below the scan threshold. The Scan Threshold and Transition Time parameters guarantee a minimum level of client roaming performance. Together with the highest expected client speed and roaming hysteresis, these parameters make it possible to design a wireless LAN network that supports roaming simply by ensuring a certain minimum overlap distance between access points. Range: 1 to 10 seconds Default: 5 seconds 

• Click Apply to commit your changes. 

• Click Save Configuration to save your changes. 

I hope it will solve your problem.

Regards