HP A5120 EI Series Configuration Manual page 65

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