3Com CoreBuilder 3500, Руководство по внедрению

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130 C
HAPTER
7: B
RIDGE
-W
IDE AND
B
RIDGE
P
ORT
P
ARAMETERS
Figure 24 illustrates the factors that cause a port to change from one
state to another. The arrows indicate the direction of movement between
states. The numbers correspond to the factors that affect the transition.
Figure 24 Factors in Spanning Tree Port State Transitions
As shown in Figure 24, for a port in the blocking state to transition to the
listening state, STP must select that port as a designated or root port.
After the port enters the listening state, forward delay must expire before
the port can transition to the learning state. Then another forward delay
period must expire (listening state) before the port can transition to the
forwarding state. If you disable a port in the listening, learning, or
forwarding state or if port initialization fails, then that port becomes
disabled.
Disabled Blocking Listening Learning Forwarding
Port enabled by either network administrator or initialization
Port disabled by either network administrator or failure
Spanning Tree algorithm selects port as designated or root
Spanning Tree algorithm does not select port as designated or root
Forwarding timer (forward delay) expires
and 1 2
1
2
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4
5 5
1
5
2
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