Installation manual

Operation Manual - STP
Quidway S3000-EI Series Ethernet Switches Chapter 1
MSTP Region-configuration
Huawei Technologies Proprietary
1-9
Switch A
with pri
ority 0
Switch C
with priority 2
Switch B
with priority 1
CP2
BP2
BP1
AP1
4
5
Figure 1-5 The final stabilized spanning tree
ample is simplified. For example,
in actual calculation should comprise both
switch priority and switch MAC address. Designated port ID should comprise port
es as the roots. The
gnate s at a regular interval of
U, the switch will
ht away, so the old root ports and designated ports that have
not detected the topology change will still forward the data through the old path. If the
e some features easy to
manage from the point of view of the users. These features include root bridge hold,
To facilitate the descriptions, the description of the ex
the root ID and the designated switch ID
priority and port MAC address. In the updating process of a configuration BPDU, other
configuration BPDUs besides the first four items will make modifications according to
certain rules. The basic calculation process is described below:
z Configuration BPDU forwarding mechanism in STP:
Upon the initiation of the network, all the switches regard themselv
desi d ports send the configuration BPDUs of local port
HelloTime. If it is the root port that receives the configuration BPD
enable a timer to time the configuration BPDU as well as increase MessageAge carried
in the configuration BPDU by certain rules. If a path goes wrong, the root port on this
path will not receive configuration BPDUs any more and the old configuration BPDUs
will be discarded due to timeout. Hence, recalculation of the spanning tree will be
initiated to generate a new path to replace the failed one and thus restore the network
connectivity.
However, the new configuration BPDU as now recalculated will not be propagated
throughout the network rig
new root port and designated port begin to forward data immediately after they are
elected, an occasional loop may still occur. In RSTP, a transitional state mechanism is
thus adopted to ensure the new configuration BPDU has been propagated throughout
the network before the root port and designated port begin to send data again. That is,
the root port and designated port should undergo a transitional state for a period of
Forward Delay before they enter the forwarding state.
MSTP is compatible with STP and RSTP. The MSTP switch can recognize both the
STP and RSTP packets and calculate the spanning tree with them. Beside the basic
MSTP functions, Quidway Ethernet Switch Series also provid