STP Configuration
146
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
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 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}
By 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}
Next, port CP2 receives the updated configuration BPDU of Device
B {0, 5, 1, BP2}. Because the received configuration BPDU is
superior to its old one, Device C launches a BPDU update
process.
At the same time, port CP1 receives configuration BPDUs
periodically from Device A. Device C does not launch an update
process after comparison.
CP1: {0, 0, 0, AP2}
CP2: {0, 5, 1, BP2}
Summary of Contents for S6424-S2C2 series
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