change my E1 status to learning and will begin to add address
table entries learned from frames entering my E1 interface. I will
not forward frames out my E1 interface yet, nor will I forward
frames that enter E1 yet.
timer expires, I will change my E1 status to forwarding.
segments. The intermediate states are used in an effort to reduce the possibility of temporary
loops. Table 4-13 summarizes the intermediate states of the Spanning Tree.
which bridge is root. In listening state, all that matters is listening for CBPDUs so that a new
choice for root and designated bridge can be made. In learning state, MAC addresses can be
learned based on incoming frames.
out yet (see Table 4-12). The Spanning-Tree Protocol includes the concept of notifying all
bridges that a tree change has occurred, allowing the bridges to quickly time out address table
entries. By doing so, the new path can be used very quickly.
its logic (shown in the list following Figure 4-20). The topology change message is received by
the root because each intervening bridge is tasked with forwarding the message. The root reacts
by setting a topology change flag in its CBPDUs for a period of time. Because all bridges
propagate these messages, all bridges will notice the topology change flag in the CBPDU. Each
bridge can then choose to use a shorter time (for example, 2 seconds) to time out address table
entries.
Frames?
Received Frames?
Stable State?