Specifications

Functions
102
4.4 Spanning Tree Algorithm
RS2-4R
Release 1.0 03/04
D It must produce a reproducible topology that can be pre-defined by
management.
D It must be transparent to the terminal equipment.
D By creating a tree structure it must result in a low network load compared
to the available transmission capacity.
4.4.2 Rules for creating the tree structure
Each bridge is uniquely described by the following parameters:
D Bridge identification
D Root path costs
D Port identification
U Bridge identification
The bridge identification is 8 bytes long. The 6 low-value bytes are for-
med by the 48-bit Ethernet address. This ensures that each bridge has a
unique identification. The higher-value parts of the bridge identification
are formed by the priority number which can be changed by the manage
-
ment administrator when configuring the network. The bridge with the
numerically lowest-value bridge identification has the highest priority.
The MAC address and priority are kept in the Management Information
Base (see
“dot1dBridge (1.3.6.1.2.1.17)” on page 316):
- dot1dBaseBridgeAddress (1.3.6.1.2.1.17.1.1.0)
- dot1dStpPriority (1.3.6.1.2.1.17.2.2.0)
Fig. 31: Bridge identification
Ethernet AddressPriority
LSBMSB