H3C Technologies H3C S12500 Series Switches - Manual (Page 72)

59
Device Comparison process
Configuration BPDU
on ports after
comparison
• 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 out the calculated configuration BPDU.
• Root port (Port B1):
{0, 0, 0, Port A1}
• Designated port (Port
B2): {0, 5, 1, Port B2}
Device C
• Port C1 receives the configuration BPDU of Port A2 {0, 0, 0,
Port A2}, finds that the received configuration BPDU is
superior to its existing configuration BPDU {2, 0, 2, Port C1},
and updates its configuration BPDU.
• Port C2 receives the original configuration BPDU of Port B2
{1, 0, 1, Port B2}, finds that the received configuration BPDU
is superior to the existing configuration BPDU {2, 0, 2, Port
C2}, and updates its configuration BPDU.
• Port C1: {0, 0, 0, Port
A2}
• Port C2: {1, 0, 1, Port
B2}
• Device C compares the configuration BPDUs of all its ports,
decides that the configuration BPDU of Port C1 is the
optimum, and selects Port C1 as the root port with the
configuration BPDU unchanged.
• Based on the configuration BPDU and path cost of the root
port, Device C calculates the configuration BPDU of Port C2
{0, 10, 2, Port C2}, and compares it with the existing
configuration BPDU of Port C2 {1, 0, 1, Port B2}. Device C
finds that the calculated configuration BPDU is superior to
the existing one, selects Port C2 as the designated port, and
replaces the configuration BPDU of Port C2 with the
calculated one.
• Root port (Port C1):
{0, 0, 0, Port A2}
• Designated port (Port
C2): {0, 10, 2, Port
C2}
• Port C2 receives the updated configuration BPDU of Port B2
{0, 5, 1, Port B2}, finds that the received configuration BPDU
is superior to its existing configuration BPDU {0, 10, 2, Port
C2}, and updates its configuration BPDU.
• Port C1 receives a periodic configuration BPDU {0, 0, 0, Port
A2} from Port A2, finds that it is the same as the existing
configuration BPDU, and discards the received one.
• Port C1: {0, 0, 0, Port
A2}
• Port C2: {0, 5, 1, Port
B2}