QTech QSW-3900, Руководство пользователя

Страница: 191 / 245

QTECH Software Configuration Manual
15-190
Device Comparison process
BPDU of port after
comparison
Device A
·
Port AP1 receives the configuration BPDU of Device
B {1, 0, 1, BP1}. Device A finds that the
configuration BPDU of the local port {0, 0, 0, AP1}
is superior to the configuration received message, and
discards the received configuration BPDU.
·
Port AP2 receives the configuration BPDU of Device
C {2, 0, 2, CP1}. Device A finds that the BPDU of
the local port {0, 0, 0, AP2} is superior to the
received configuration BPDU, and discards the
received configuration BPDU.
·
Device A finds that both the root bridge and
designated bridge in the configuration BPDUs of all
its ports are Device A itself, so it assumes itself to be
the root bridge. In this case, it does not make any
change to the configuration BPDU of each port, and
starts sending out configuration BPDUs periodically.
AP1 : {0, 0, 0,
AP1}
AP2 : {0, 0, 0,
AP2}
·
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
discards the received configuration BPDU.
BP1 : {0, 0, 0,
AP1}
BP2 : {1, 0, 1,
BP2}
Device B
·
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 computed configuration
BPDU {0, 5, 1, BP2} with the configuration BPDU of
BP2. If the computed BPDU is superior, BP2 will act
as the designated port, and the configuration BPDU
on this port will be replaced with the computed
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 message
was updated. Device C finds that the received
configuration BPDU is superior to the configuration
BPDU of the local port {2, 0, 2, CP2}, and updates
the configuration BPDU of CP2.
CP1 : {0, 0, 0,
AP2}
CP2 : {1, 0, 1,
BP2}