HP A5120 EI Series

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Figure 16 provides an example of how the STP algorithm works.
Figure 16 Network diagram for the STP algorithm
Device A
Priority = 0
Device B
Priority = 1
Device C
Priority = 2
Port A1 Port A2
Port B1
Port B2
Port C1
Port C2
P
ath cost
=
5
P
ath cost
=
10
Path cost = 4
As shown in Figure 16, the priority of Device A, Device B, and Device C is 0, 1, and 2 respectively, and
the path costs among these links are 5, 10, and 4 respectively.
4. Initial state of each device
Table 10 Initial state of each device
Device
Port name
Configuration BPDU on the
port
Device A
Port A1
{0, 0, 0, Port A1}
Port A2
{0, 0, 0, Port A2}
Device B
Port B1
{1, 0, 1, Port B1}
Port B2
{1, 0, 1, Port B2}
Device C
Port C1
{2, 0, 2, Port C1}
Port C2
{2, 0, 2, Port C2}
NOTE:
In Table 10, each configuration BPDU contains the following fields: root bridge ID, root path cost,
designated bridge ID, and designated port ID.
5. Comparison process and result on each device