Symbol Clients & Cisco 350 APs

[ertrqueen]

I've got a customer using Symbol 6948 clients w/Cisco 350 APs running 11.07. It appears that the Symbol clients seem to always want to go to the AP that's on Channel 1, even though there's much closer APs that are on channels 6 or 11. All the APs are set to run 11Mb data rate only, and the site survey was done using Cisco clients. Symbol has stated that these devices are fully 802.11b compliant, however, the tendency to choose Channel 1 looks more like frequency hopping. Has anyone else had any experience w/these Symbol devices??

Thanks...........Janet

[rjs]

I also have a cust w/three 350AP was on 11.06 now 11.07 and Symbol barcode scanners (sorry I don't have model w/me). 1st it is my understanding that a wlan device will not leave an AP until out of range, is it possible your AP channel 1 is cover most of your wireless area? Where are the 6948s turned on?

My problem is long X-wait from server to scanners. Sniffed the wireless, found high CRC errors usually from the farthest away AP. Wireless devices are also reassociating non stop. Has anyone sniffed wireless, are CRCs normal?

[gavl]

This one goes out to the CCIE that posted.

If when you look at the AP logs it shows that the clients have Authenticated , Associated , Roamed in very quick succession (several times a second) and as you say the server response times from the AS400 (I'm guessing there) are slow then you may have a problem with the version of radio card in the Symbol terminals.

I recently sniffed a WLAN in exactly that senario and found that the clients were sending probe requests but missing the responses 90 % of the time and causing association problems. This, coupled with the fact that Symbol clients are in control of their own roaming process gives the symptoms you may be experiencing.

The fix is to move to Trilogy 2+ radio cards

Reach me at gavinl@ryzexeurope.com

[James Strong]

Have you checked the advanced radio config on the other APs? The Symbol scanners require that "long" radio headers be turned on, or they won't associate. Also, turn off the "use Aironet extensions" radio button.

[gavl]

Firstly if you haven't done it already, clone the config from AP1 across all AP's.

There are some differences with Symbol kit in that the clients decide when to roam not the AP as with most other manufacturers. Check that the supported data rates (in the cfg11 menu from the D: prompt) on the Symbol terminals is set to 11mb only.

As mentioned here by someone else, the terminals will associate to the AP with the best RSSI value around, so if your closer to AP 1 when you boot up and your facility is not all that large then its possible that the clients are quite happy to stay with that AP.

[ertrqueen]

Don't have any control whatsoever of the Symbol devices-we have been able to get the Symbols configured for CAM, instead of PSP (since they're not using battery power), to solve another problem, but that's about it. With Symbol stating that they're compliant, the customer is pointing back to the network devices. New radios are out of the question.

The Aironet extensions are turned off, and I am using long radio headers. Symbol has also come back and said that we should not be limiting the datarate to 11Mb, but to set the datarates as follows:

1-basic 2-yes 5.5-yes 11-yes

I kind of see this solution as turning up the car radio, but it's not worth the battle. Symbol also suggested putting in a bunch of filters (allowing only 'symbol' traffic), but I was able to kill that suggestion.

I am seeing the multiple association/authentication/roaming instances - about every 2-5 seconds, when the Symbol unit is stationary, more when it's moving. And it still tries to go to Channel 1, even if it was booted up right underneath a Channel 6 or 11 AP, and the Channel 1 AP is 200+ feet away. Very weird.

Symbol also states that they do 'pre-emptive' roaming. Don't have a good explanation of what that is - kind of thought maybe it was a bug marketed as a feature??