Allied Telesis AT-9000 Series - Manual (Page 606)

Chapter 40: STP, RSTP and MSTP Protocols
578
Figure 117. Loop Guard Example 5
Switch 3
Switch 1
Old root bridge
RSTP stops operating
Port 4
Loop guard changes the
port to the blocking state
from the forwarding state
Switch 2
New root bridge
Port 14
Transitions from the blocking state
to the forwarding state