Wireless Access

I have recently come across some interesting behaviour by some Verifone payment terminals.  Seemingly these devices only sent probe requests when first attempting to connect to the wifi.  After they connect, they don't probe again....or at least they didn't for the 12 mins I was running a wireless capture.

This kind of explains some curious behaviour we were seeing with them.  It seems when they boot, whatever they see at the time is the only APs they will connect to from that point.  So some sites were booting them up in the back office where they could only see 1 AP and then there were connectivity issues when they were taken out onto the shop floor.  Rebooting them made them connect again.

Anyhow, my question is around client-match and what the impact of this behaviour would be? 

Should client-match be disabled in this case?

"After they connect, they don't probe again" -  Are you saying that they connect to an access point and stay on it?  Well if they do that, clientmatch would not kick in, as long as their signal stayed acceptable and no other access point saw them at 10db better (sticky).  Why would ClientMatch need to be disabled?

They do roam apparently.  It's like when they first boot, they will scan and whatever they see at the time is the only aps they will connect to from that point on.

I was doing some testing and when we swapped an AP the devices did not reconnect.  Rebooting it made it connect, which got me thinking about the probes.......

I've not seen this behaviour in a client before which is the reason for my question about client match.

Based on what you are saying, clientmatch would not kick in, if it had a good connection already.

Additionally, should it associate to aa:aa, and then for some reason aa:aa goes down and bb:bb is the next closest AP, if the Verifone device won't probe for a new BSSID, Clientmatch will have nothing to steer anyway. The client has to ask for something and if it's not, it's a severe device issue that Verifone should look at.

We had similar issues YEARS ago with some handhelds that when they powered up would build a BSSID list of available APs, but once roamed outside of that and didn't see them anymore, would fail to associate. The kicker was with a wireless sniff, we would see the probes going out and the responses being sent back, but the handheld would just ignore all the probe responses. Vendor provided a fix (that led to another bug of a limit to the roam table), but that was a fun one.

Jerrod, thanks for the input.  Yes, the joys of working with these old handhelds. ;-)

We have raised with Verifone, but no response.  I'm guessing they will say its a 'power saving optimisation' or something like that.