PLANET GSW-1602SF - Manual (Page 84)

User’s Manual of GSW-1602SF / GSW-2404SF
The Hello Time cannot be longer than the Max. Age. Otherwise, a configuration error will
occur.
Observe the following formulas when setting the above parameters:
Max. Age _ 2 x (Forward Delay - 1 second)
Max. Age _ 2 x (Hello Time + 1 second)
The following are the user-configurable STP parameters for the port or port group level:
Variable Description Default Value
Port Priority A relative priority for each
port –lower numbers give a higher priority
and a greater chance of a given port being
elected as the root port
128
Port Cost A value used by STP to evaluate paths –
STP calculates path costs and selects the
path with the minimum cost as the active
path
200,000-100Mbps Fast Ethernet ports
20,000-1000Mbps Gigabit Ethernet
ports
0 - Auto
Default Spanning-Tree Configuration
Feature Default Value
Enable state STP disabled for all ports
Port priority 128
Port cost 0
Bridge Priority 32,768
3. Illustration of STP
A simple illustration of three switches connected in a loop is depicted in the below diagram. In this example, you can
anticipate some major network problems if the STP assistance is not applied.
If switch A broadcasts a packet to switch B, switch B will broadcast it to switch C, and switch C will broadcast it to back to
switch A and so on. The broadcast packet will be passed indefinitely in a loop, potentially causing a network failure. In this
example, STP breaks the loop by blocking the connection between switch B and C. The decision to block a particular
connection is based on the STP calculation of the most current Bridge and Port settings.
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