R3166-R3206-HP High-End Firewalls Network Management Configuration Guide-6PW101

48
Device Comparison process
BPDU of port
after com
p
arison
Device B
• Port BP1 receives the configuration BPDU of Device A {0, 0, 0, AP1}.
Device B finds that the received configuration BPDU is superior to the
configuration BPDU of the local port {1, 0, 1, BP1}, and updates the
configuration BPDU of BP1.
• Port BP2 receives the configuration BPDU of Device C {2, 0, 2, CP2}.
Device B finds that the configuration BPDU of the local port {1, 0, 1,
BP2} is superior to the received configuration BPDU, and therefore
discards the received configuration BPDU.
BP1: {0, 0, 0, AP1}
BP2: {1, 0, 1, BP2}
• Device B compares the configuration BPDUs of all its ports, and
determines that the configuration BPDU of BP1 is the optimum
configuration BPDU. Then, it uses BP1 as the root port, the configuration
BPDUs of which will not be changed.
• Based on the configuration BPDU of BP1 and the path cost of the root
port (5), Device B calculates a designated port configuration BPDU for
BP2 {0, 5, 1, BP2}.
• Device B compares the calculated configuration BPDU {0, 5, 1, BP2}
with the configuration BPDU of BP2. If the calculated BPDU is superior,
BP2 will act as the designated port, and the configuration BPDU on this
port will be replaced with the calculated configuration BPDU, which will
be sent out periodically.
Root port BP1:
{0, 0, 0, AP1}
Designated port
BP2:
{0, 5, 1, BP2}
Device C
• Port CP1 receives the configuration BPDU of Device A {0, 0, 0, AP2}.
Device C finds that the received configuration BPDU is superior to the
configuration BPDU of the local port {2, 0, 2, CP1}, and updates the
configuration BPDU of CP1.
• Port CP2 receives the configuration BPDU of port BP2 of Device B {1, 0,
1, BP2} before the configuration BPDU is updated. Device C finds that
the received configuration BPDU is superior to the configuration BPDU
of the local port {2, 0, 2, CP2}, and therefore updates the configuration
BPDU of CP2.
CP1: {0, 0, 0, AP2}
CP2: {1, 0, 1, BP2}
After comparison:
• The configuration BPDU of CP1 is elected as the optimum configuration
BPDU, so CP1 is identified as the root port, the configuration BPDUs of
which will not be changed.
• Device C compares the calculated designated port configuration BPDU
{0, 10, 2, CP2} with the configuration BPDU of CP2, and CP2 becomes
the designated port, and the configuration BPDU of this port will be
replaced with the calculated configuration BPDU.
Root port CP1:
{0, 0, 0, AP2}
Designated port
CP2:
{0, 10, 2, CP2}
• Then, port CP2 receives the updated configuration BPDU of Device B
{0, 5, 1, BP2}. Because the received configuration BPDU is superior to
its own configuration BPDU, Device C launches a BPDU update
process.
• At the same time, port CP1 receives periodic configuration BPDUs from
Device A. Device C does not launch an update process after
comparison.
CP1: {0, 0, 0, AP2}
CP2: {0, 5, 1, BP2}