Spanning tree protocol operation – Cabletron Systems SmartSTACK ELS100 User Manual
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Spanning Tree Concepts 79
Table B-1. Spanning Tree Protocol Defaults
For detailed information on the operation of the Spanning Tree Protocol, 
consult Section 4 of IEEE Standard 802.1D, ISO/IEC 10038:1993.
Spanning Tree Protocol Operation
When the Spanning Tree Protocol is enabled for the first time or when 
there is a change in the network topology, such as a failure or the addition 
or removal of a component, the Spanning Tree Protocol automatically 
sets up the active topology of the current network.
Parameter
Description
Default Value
Bridge 
Group 
Address
Unique MAC group address, recognized by all bridges 
in the network.
Bridge 
Identifier
Identifier for each bridge. This parameter consists of 
two parts: a 16-bit bridge priority and a 48-bit network 
adapter address. Ports are numbered in absolute 
numbers starting from 1 regardless of their bridge 
attachment. The network adapter address is the same 
address as the first port of the bridge.
32768 (bridge 
priority)
Port 
Identifier
Identifies each port of each bridge, with an incremen-
tal default value given for each port.
Port 1 -32768
Port 9 -32776
Port 17 -32784
Port 2 -32769
Port 10 -32777
Port 18 -32785
Port 3 -32770
Port 11 -32778
Port 19 -32786
Port 4 -32771
Port 12 -32779
Port 20 -32787
Port 5 -32772
Port 13 -32780
Port 21 -32788
Port 6 -32773
Port 14 -32781
Port 22 -32789
Port 7 -32774
Port 15 -32782
Port 23 -32790
Port 8 -32775
Port 16 -32783
Port 24 -32791
Port Priority
Indicates the priority of a specific port in relation to 
other ports.
128
Cost 
Component 
of Each Port
The Spanning Tree Protocol calculates and ensures 
that an active topology generates minimal cost paths. 
A value of 100 is generally used for 10Mbps Ethernet 
networks and a value of 10 is generally used for 
100Mbps Ethernet networks.
10
