User Manual

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Users Manual of XGS-6350-24X4C
root.
(4) Each MSTI can independently choose a switch as the MSTI regional root.
(5) Each switch in the region and the LAN segment can decide the minimum cost path to the MSTI root.
(6) The root port of CIST provides the minimum-cost path between the CIST regional root and the CIST
root.
(7) The designated port of the CIST provided its LAN with the minimum-cost path to the 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 MSTI regional 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 master port of all MSTI in the region.
19.2.1.7 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 uses Hop Count to calculate the network
topology.
To prevent information from looping, MSTP relates the transmitted information to the attribute 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 each receiving 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.
19.2.1.8 STP Compatibility
MSTP allows the switch to work with the traditional STP switch through protocol conversion 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 port that receives the STP information is then considered as a boundary port.
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 mstp migration-check to clear the STP
message that the port learned, and make the port to return to the MSTP state.
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.
19.2.2 MSTP Configuration Task List
 Default MSTP configuration
 Enabling and disabling MSTP
 Configuring MSTP region
 Configuring network root