User's Manual
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(7) The designated port of the CIST provided its LAN with the minimum-cost path tothe CIST
root.
(8) The Alternate port and the Backup port provides connection when the switch,port or the LAN
does not work or is removed.
(9) The MSTI root port provides the minimum cost path to the MSTI regional root.
(10) The designated port of MSTI provides the minimum cost path to the MSTIregional root.
(11) A master port provides the connection between the region and the CIST root. In the region,
the CIST root port of the CIST regional root functions as the masterport of all MSTI in the
region.
36.1.7 Hop Count
Different from STP and RSTP, the MSTP protocol does not use Message Age and Max Age in the BPDU
configuration message to calculate the network topology. MSTP usesHop Count to calculate the network
topology.
To prevent information from looping, MSTP relates the transmitted information to theattribute of hop count in
each spanning tree. The attribute of hop count for BPDU is designated by the CIST regional root or the MSTI
regional root and reduced in eachreceiving port. If the hop count becomes 0 in the port, the information will be
dropped and then the port turns to be a designated port.
36.1.8 STP Compatibility
MSTP allows the switch to work with the traditional STP switch through protocolconversion mechanism. If one
port of the switch receives the STP configuration message, the port then only transmits the STP message. At
the same time, the portthat receives the STP information is then considered as a boundary port.
Note:
When a port is in the STP-compatible state, the port will not automatically resume to the MSTP
state even if the port does not receive the STP message any more. In this case, you can run
spanning-tree mstpmigration-check to clear the STP message that the port learned, and make
the port to return to the MSTPstate.
The switch that runs the RSTP protocol can identify and handle the MSTP message. Therefore, the MSTP
switch does not require protocol conversion when it works with the RSTP switch.
36.2 MSTP Configuration Task List
Default MSTP Configuration
Enabling and disabling MSTP
Configuring MSTP region
Configuring network root
Configuring secondary root
Configuring bridge priority
Configuring time parameters of STP
Configuring network diameter
Configuring maximum hop count
Configuring port priority
Configuring path cost for port