User's Manual

260
CIST Root Identifier 6 – 13
CIST External Root Path Cost 14 – 17
CIST Regional Root Identifier 18 – 25
CIST Port Identifier 26 – 27
Message Age 28 – 29
Max Age 30 – 31
Hello Time 32 – 33
Forward Delay 34 – 35
Version 1 Length 36
Version 3 Length 37 – 38
Format Selector 39
Configuration Name 40 – 71
Revision 72 – 73
Configuration Digest 74 – 89
CIST Internal Root Path Cost 90 – 93
CIST Bridge Identifier 94 – 101
CIST Remaining Hops 102
MSTI Configuration Messages 103 ~
Table 2.2 MST configuration information
Field Name Byte Number
MSTI FLAGS 1
MSTI Regional Root Identifier 2 – 9
MSTI Internal Root Path Cost 10 – 13
MSTI Bridge Priority 14
MSTI Port Priority 15
MSTI Remaining Hops 16
36.1.6 Stable State
The MSTP switch performs calculation and compares operations according to thereceived BPDU, and finally
ensures that:
(1) One switch is selected as the CIST root of the whole network.
(2) Each switch and LAN segment can decide the minimum cost path to the CIST root, ensuring
a complete connection and prevent loops.
(3) Each region has a switch as the CIST regional root. The switch has the minimumcost path
to the CIST 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 costpath to the
MSTI root.
(6) The root port of CIST provides the minimum-cost path between the CISTregional root and
the CIST root.