HP 6125G HP 6125G & 6125G/XG Blade Switches Layer 2 - LAN Switching Co - Page 63

Device, Port name, Configuration BPDU on the port, Comparison process, ports after comparison

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Device Device B Device C Port name Port A2 Port B1 Port B2 Port C1 Port C2 Configuration BPDU on the port {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} 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 Table 11 Comparison process and result on each device Device Device A Device B Comparison process • Port A1 receives the configuration BPDU of Port B1 {1, 0, 1, Port B1}, finds that its existing configuration BPDU {0, 0, 0, Port A1} is superior to the received configuration BPDU, and discards the received one. • Port A2 receives the configuration BPDU of Port C1 {2, 0, 2, Port C1}, finds that its existing configuration BPDU {0, 0, 0, Port A2} is superior to the received configuration BPDU, and discards the received one. • Device A finds that it is both the root bridge and designated bridge in the configuration BPDUs of all its ports, and considers itself as the root bridge. It does not change the configuration BPDU of any port and starts to periodically send configuration BPDUs. • Port B1 receives the configuration BPDU of Port A1 {0, 0, 0, Port A1}, finds that the received configuration BPDU is superior to its existing configuration BPDU {1, 0, 1, Port B1}, and updates its configuration BPDU. • Port B2 receives the configuration BPDU of Port C2 {2, 0, 2, Port C2}, finds that its existing configuration BPDU {1, 0, 1, Port B2} is superior to the received configuration BPDU, and discards the received one. • Device B compares the configuration BPDUs of all its ports, decides that the configuration BPDU of Port B1 is the optimum, and selects Port B1 as the root port with the configuration BPDU unchanged. • Based on the configuration BPDU and path cost of the root port, Device B calculates a designated port configuration BPDU for Port B2 {0, 5, 1, Port B2}, and compares it with the existing configuration BPDU of Port B2 {1, 0, 1, Port B2}. Device B finds that the calculated one is superior, decides that Port B2 is the designated port, replaces the configuration BPDU on Port B2 with the calculated one, and periodically sends the calculated configuration BPDU. Configuration BPDU on ports after comparison • Port A1: {0, 0, 0, Port A1} • Port A2: {0, 0, 0, Port A2} • Port B1: {0, 0, 0, Port A1} • Port B2: {1, 0, 1, Port B2} • Root port (Port B1): {0, 0, 0, Port A1} • Designated port (Port B2): {0, 5, 1, Port B2} 54

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54
Device
Port name
Configuration BPDU on the port
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
Table 11
Comparison process and result on each device
Device
Comparison process
Configuration BPDU on
ports after comparison
Device A
•
Port A1 receives the configuration BPDU of Port B1 {1, 0, 1, Port
B1}, finds that its existing configuration BPDU {0, 0, 0, Port A1}
is superior to the received configuration BPDU, and discards the
received one.
•
Port A2 receives the configuration BPDU of Port C1 {2, 0, 2, Port
C1}, finds that its existing configuration BPDU {0, 0, 0, Port A2}
is superior to the received configuration BPDU, and discards the
received one.
•
Device A finds that it is both the root bridge and designated
bridge in the configuration BPDUs of all its ports, and considers
itself as the root bridge. It does not change the configuration
BPDU of any port and starts to periodically send configuration
BPDUs.
•
Port A1: {0, 0, 0, Port
A1}
•
Port A2: {0, 0, 0, Port
A2}
Device B
•
Port B1 receives the configuration BPDU of Port A1 {0, 0, 0, Port
A1}, finds that the received configuration BPDU is superior to its
existing configuration BPDU {1, 0, 1, Port B1}, and updates its
configuration BPDU.
•
Port B2 receives the configuration BPDU of Port C2 {2, 0, 2, Port
C2}, finds that its existing configuration BPDU {1, 0, 1, Port B2}
is superior to the received configuration BPDU, and discards the
received one.
•
Port B1: {0, 0, 0, Port
A1}
•
Port B2: {1, 0, 1, Port
B2}
•
Device B compares the configuration BPDUs of all its ports,
decides that the configuration BPDU of Port B1 is the optimum,
and selects Port B1 as the root port with the configuration BPDU
unchanged.
•
Based on the configuration BPDU and path cost of the root port,
Device B calculates a designated port configuration BPDU for
Port B2 {0, 5, 1, Port B2}, and compares it with the existing
configuration BPDU of Port B2 {1, 0, 1, Port B2}. Device B finds
that the calculated one is superior, decides that Port B2 is the
designated port, replaces the configuration BPDU on Port B2
with the calculated one, and periodically sends the calculated
configuration BPDU.
•
Root port (Port B1): {0,
0, 0, Port A1}
•
Designated port (Port
B2): {0, 5, 1, Port B2}