Recently I had to reset my Fonera 2.0 WLAN router. I reconfigured it immediately with the same private SSID, security mode (WPA2-PSK) and key. However, when I looked at my Windows notebooks, they were not automatically connected to the new/old network. Unfortunately I did not take a screenshot, but it showed a red symbol next to the SSID (with a red X). My WLAN printer and my Android phone lost their connection, too, and failed to regain it.
I was under the impression that identical settings on identical hardware should lead to identical results. I expected my network devices to recognize the new settings as the old and reconnect automatically.
An answer on Superuser (http://superuser.com/questions/122441/multiple-access-points-for-the-same-ssid) states:
Many clients assume that these kinds of settings will be the same across all APs with the same SSID.
It further suggests to vary the channel between two APs. I did leave the channel selection before and after the reset on automatic, so this should have had no influence.
All my clients - printer, smartphone, notebooks - failed to recognise the network after reinstalling it with identical settings. Why was this the case? Could it be the router that sends a different signature or uses a different certificate after the reset (if something like that exists)?
January 2012 edit:
Here's some more food for thought. After switching from my Fonera to a Zyxel 660 HN modem-router with identical WiFi settings most of my devices - Android smart phones, one Ubuntu netbook, an HP printer, an old notebook with a plain vanilla windows 7 - gladly accepted the new network without reconfiguration. A newer HP notebook with Windows 7 did not - though it has HP crapware installed that "manages" my network connections.