paths to be available. In this case, Bridge 3's E1 will need to change from a blocking to
forwarding state, which has not occurred yet. The key part of the upcoming logic is based on
this corollary of Spanning Tree:
from blocking to forwarding, or vice versa.
table entries refer to the path that has failed. Table 4-12 refers to the address table entries for
0200.0000.AAAA in all five bridges, showing that four of the five bridge address tables refer
to the failed path. Use Table 4-12 in conjunction with Figure 4-20 to verify that the path to this
MAC address is still invalid.
state on its E1 interface. Bridge 3's reaction to the lack of CBPDUs from Bridge 4 causes this
change to occur. Consider the logic that Bridge 3 uses in this case:
designated bridge has failed. I will become the designated bridge
on the LAN segment to which E1 is attached because no other
bridges are forwarding CBPDUs onto that segment.
That means that I will not learn addresses based on frames
entering E1. I will not forward frames entering E1, nor will I
forward frames out E1.
(typically a few seconds).
change is being made. (The root will eventually receive the
message.)