Allied Telesis AT-S63 - Manual (Page 656)

Chapter 28: 802.1x Port-based Network Access Control
656 Section IV: Port Security
ˆ When 802.1x Port-based Network Access Control is activated on a
switch, the feature polls all RADIUS servers specified in the RADIUS
configuration. If three servers have been configured, the switch polls
all three. If server 1 responds, all future requests go only to that server.
If server 1 stops responding, the switch again polls all RADIUS
servers. If server 2 responds, but not server 1, then all future requests
go to servers 1 and 2. If only server 3 responds, then all future
requests go to all three servers.