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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 topol ogy, su ch as a fail ure or the a dditio n

or removal of a compon ent, the Spanning Tre e Protocol automati cally

sets up the active topology of the current network.

Parameter Description Default Value
Bridge
Group
Address
Unique MAC group address, recognized by al l b ridges
in the network.
Bridge
Identifier Identifier for each bridge. This parameter consis ts 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 10 -32777 Port 19 -32786
Port 2 -32769 Port 11 -32778 Port 20 -32787
Port 3 -32770 Port 12 -32779 Port 21 -32788
Port 4 -32771 Port 13 -32780 Port 22 -32789
Port 5 -32772 Port 14 -32781 Port 23 -32790
Port 6 -32773 Port 15 -32782 Port 24 -32791
Port 7 -32774 Port 16 -32783 Port 25 -32792
Port 8 -32775 Port 17 -32784 Port 26 -32793
Port 9 -32776 Port 18 -32785
Port Priority Indicates the priority of a specific port in relation to
other ports. 128
Cost Compo-
nent 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, a value of 10 is for 100Mbps Ethernet
networks, and a value of 1 is for 1Gbps Ethernet
networks.
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