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GS752TP, GS728TP, and GS728TPP Gigabit Smart Switches
CST Configuration
To configure Common Spanning Tree (CST) and Internal Spanning Tree on the switch, use
the CST Configuration screen.
To configure CST settings:
1. Select Switching STP Advanced CST Configuration.
The following screen displays:
2. Specify values for CST in the following fields:
•Bridge Priority. Specify the bridge priority value for the Common and Internal
Spanning Tree (CST). When switches or bridges are running STP, each is assigned a
priority. After exchanging BPDUs, the switch with the lowest priority value becomes
the root bridge. The bridge priority is a multiple of 4096. If you specify a priority that is
not a multiple of 4096, the priority is automatically set to the next lowest priority that is
a multiple of 4096. For example, if you set the priority to any value from 0 through
4095, it is set to 0. The valid range is 0–61440. The default priority is 32768.
•Bridge Max Age (Sec). Specify the bridge maximum age time for the Common and
Internal Spanning Tree (CST), which indicates the amount of time in seconds a bridge
waits before implementing a topological change. The value must be less than or equal
to (2 * bridge forward delay) – 1 and greater than or equal to 2 * (bridge hello time +1).
The valid range is 6–40, and the default value is 20.
•Bridge Hello Time (Sec). Specifies the switch hello time for the Common and
Internal Spanning Tree (CST), which indicates the amount of time in seconds a root
bridge waits between configuration messages. The value is fixed at 2 seconds.
•Bridge Forward Delay (Sec). Specify the switch forward delay time, which indicates
the amount of time in seconds a bridge remains in a listening and learning state
before forwarding packets. The value must be greater or equal to (bridge max age / 2)
+ 1. The valid range is 4–30 seconds. The default value is 15.