Interlogix GE-DSSG-244-POE User Manual - Manual (Page 117)

IFS NS3601-24P/4S GE-DSSG-244 and 244-POE User Manual
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2. STP Parameters
STP Operation Levels
The Switch allows for two levels of operation: the switch level and the port level. The switch level forms a spanning tree consisting of
links between one or more switches. The port level constructs a spanning tree consisting of groups of one or more ports. The STP
operates in much the same way for both levels.
On the switch level, STP calculates the Bridge Identifier for each switch and then sets the Root
Bridge and the Designated Bridges.
On the port level, STP sets the Root Port and the Designated Ports.
The following are the user-configurable STP parameters for the switch level:
Parameter Description Default Value
Bridge Identifier(Not user
configurable
except by setting priority
below)
A combination of the User-set priority and
the switch’s MAC address.
The Bridge Identifier consists of two parts:
a 16-bit priority and a 48-bit Ethernet MAC
address 32768 + MAC 32768 + MAC
Priority
A relative priority for each switch – lower
numbers give a higher priority and a greater
chance of a given switch being elected as
the root bridge 32768
Hello Time The length of time between broadcasts of
the hello message by the switch 2 seconds
Maximum Age Timer
Measures the age of a received BPDU for a
port and ensures that the BPDU is discarded
when its age exceeds the value of the
maximum age timer. 20 seconds
Forward Delay Timer
The amount time spent by a port in the
learning and listening states waiting for a
BPDU that may return the port to the
blocking state. 15 seconds
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
User-Changeable STP Parameters
The Switch’s factory default setting should cover the majority of installations. However, it is advisable to keep the default settings as
set at the factory; unless, it is absolutely necessary. The user changeable parameters in the Switch are as follows:
Priority
– A Priority for the switch can be set from 0 to 65535. 0 is equal to the highest Priority.
Hello Time – The Hello Time can be from 1 to 10 seconds. This is the interval between two transmissions of BPDU packets sent by
the Root Bridge to tell all other Switches that it is indeed the Root Bridge. If you set a Hello Time for your Switch, and it is not the
Root Bridge, the set Hello Time will be used if and when your Switch becomes the Root Bridge.