Windows XP WEP Authentication

When you have several access points set up to use the same WEP key,
each will implement added optimization routines so that the wireless
NIC will try to execute 802.11 authentication using the WEP key
received from the original access point as the shared key. Once this routine
is successful, the access point will instantaneously add that station
to its authenticated list of stations. However, if the authentication routine
fails, the NIC will open up to authenticate that access point and finish
its 802.11 authentication.

The access point needs to be able to determine if a station that has
openly been authenticated to the access point can effectively complete
the 802.11 authentication. This means that the access point must be
able to determine whether a station is “open authenticated” or executed
with “shared-key authentication.When the station does acquire access to the new access point using “shared key authentication,” then the 802.11 authentication routine is
still started by the new access point so that it can update its record-keeping
system. When you initiate wireless station network connectivity
through shared-key authentication, the new access point will start 802.11
to make certain that the wireless station does not experience any interruption
in its network connectivity. When the wireless station is not able
to complete the 802.11 authentication successfully with the new access point, then the wireless network connectivity to the wireless station
through the controlled access point port will be killed in order to make
certain that you retain the highest possible level of network security. 214