Hirschmann GREYHOUND GRS1020, Справочное руководство

Страница: 505 / 619

Redundancy
12.3 Spanning Tree
165
UM Config GRS
Release 8.0 09/2019
Example of manipulating the root path
You can use the network plan (see figure 38) to follow the flow chart (see figure 36) for determining
the root path. The Administrator has performed the following:
• Left the default value of 32768 (8000H) for every bridge apart from bridge 1 and bridge 5, and
• assigned to bridge 1 the value 16384 (4000H), thus making it the root bridge.
• To bridge 5 he assigned the value 28672 (7000H).
The protocol blocks the path between bridge 2 and bridge 3 as a connection from bridge 3 via
bridge 2 to the root bridge would mean higher path costs.
The path from bridge 6 to the root bridge is interesting:

The bridges select the path via bridge 5 because the value 28672 for the priority in the bridge
identifier is smaller than value 32768.
Figure 38: Example of manipulating the root path
Example of manipulating the tree structure
The Management Administrator soon discovers that this configuration with bridge 1 as the root
bridge is invalid. On the paths from bridge 1 to bridge 2 and bridge 1 to bridge 3, the control packets
which the root bridge sends to every other bridge add up.
1
P-BID = 16 384
2
P-BID = 32 768
3
P-BID = 32 768
5
P-BID = 28 672
6
P-BID = 32 768
7
P-BID = 32 768
4
P-BID = 32 768
Root Bridge
Root path
Interrupted path
P-BID
Priority of the bridge identifikation (BID)
= BID without MAC Address