H3C S3100 8C SI User Manual

Operation Manual – MSTP
H3C S3100 Series Ethernet Switches Chapter 1 MSTP Configuration
1-8
Device Comparison process
BPDU of
port after
comparis
on
z 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.
z 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:
z The configuration BPDUs 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.
z 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}
Designate
d port
CP2:
{0, 10, 2,
CP2}
z 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.
z 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}
Device
C
By comparison:
z Because the root path cost of CP2 (9) (root path cost of
the BPDU (5) + path cost corresponding to CP2 (4)) is
smaller than the root path cost of CP1 (10) (root path
cost of the BPDU (0) + path cost corresponding to CP2
(10)), the BPDU of CP2 is elected as the optimum
BPDU, and CP2 is elected as the root port, the
messages of which will not be changed.
z After comparison between the configuration BPDU of
CP1 and the calculated designated port configuration
BPDU, port CP1 is blocked, with the configuration
BPDU of the port remaining unchanged, and the port
will not receive data from Device A until a spanning tree
calculation process is triggered by a new condition, for
example, the link from Device B to Device C becomes
down.
Blocked
port CP2:
{0, 0, 0,
AP2}
Root port
CP2:
{0, 5, 1,
BP2}
After the comparison processes described in the table above, a spanning tree with
Device A as the root bridge is stabilized, as shown in
Figure 1-3.

H3C S3100 8C SI Specifications

General

Brand	H3C
Model	S3100 8C SI
Category	Switch
Language	English