Looking at the wireless statistics on a TL-WR740N wireless router, I sometimes see the MAC address "00-20-00-A5-22-1A" connecting, with the current status being "STA-ASSOC".
The manual actually shows exactly this current status as example on page 52. I don't know this MAC address, and it has sent packets to the router, but I haven't seen received packets yet.
The router uses WPA/WPA2 with AES as encryption, which is what it shows when my workstation connects to the router.
Does anyone know what STA-ASSOC is, and if someone have access to the router?