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This is more of a curiosity than a problem, but in this new office I have two D-link DAP-2553's connected in a master/slave array (this just means the master keeps certain configuration options aligned with the slave). The network is set to 802.11n-only, and each AP has the same SSID and WPA2 key. The only difference is that they are on different channels (1 and 11). The WiFi network itself is working well. Users can roam around and the signal/speed is fairly consistent.

However, I notice that when I look at the 802.11 client list in the web admin page for each of the 2 APs, I see that certain clients are connected to both, for extended periods of time, but I assume they are only passing data through one of them. Not every client is seen on each AP, but at any given time the same MAC address of a WiFi adapter can be associated (and remain associated) with both APs. The client list auto-refreshes every few seconds so I believe I'm looking at the most recent rather than stale information.

One of the WiFi adapters that consistently associates with both APs is an Intel Centrino Wireless-N 1030 (laptop chip).

Is it part of the WiFi standard that more than one association per WiFi card can be established concurrently on separate APS?

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up vote 3 down vote accepted

According to the IEEE 802.11 standard, a client (called a mobile station or "STA") may be authenticated to more than one AP at a time, but can only be associated to one AP at a time.

From IEEE Std 802.11-2007, section 5.4.2.2, "Association" (page 35), 5th paragraph:

At any given instant, a STA may be associated with no more than one AP.

In your situation with your two APs on two different channels, it's even harder for a misbehaving client to maintain two associations, because it would have to be tuning its radio back and forth between those two channels constantly.

You're probably seeing stale data after all. It may be that your Centrino client doesn't do a good job of sending a Disassociate or Deauthenticate packet to the AP it's leaving when it roams to the other AP, so the AP it left may not know it left, and may wait a minute or two before giving up on it and considering it disassociated.

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Thanks, I think your answer is spot on and that the problem was stale info in the AP. I was able to roam around with a laptop using an app in the Intel PROSet Wireless tools suite that showed which AP it was currently connected to. As soon as it switched from one AP to the other AP, both web interfaces in the APs showed that the MAC address of that adapter was connected. A short while later, however, the MAC address disappeared from AP to which it had been previously connected (i.e. the one it roamed away from). –  Bobby Burgess Mar 21 '12 at 0:10
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