FORE Systems ES-2810 Ethernet Switch User's Manual
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Standard Configuration
Standard
Configuration
3.15 Spanning Tree
3.15.1 Purpose
You can change the:
• Priority given to the switch
• Maximum length of time information is retained by the switch
• Time between transmitted Configuration BPDUs
• Time the switch spends in the Listening and Learning states
3.15.2 Warning When Using VLANs
It is important to be aware of problems that may arise when using Spanning Tree and VLANs.
The Spanning Tree can use alternative paths (such as different ports) to get messages to their
destination.
Figure 3.12 -
Spanning Tree Blocking to Prevent Loops
The diagram above, shows two switches. On the left, we see the two switches connected and
the ports are grouped in two VLANs: A and B. On the right, we have enabled STP; STP blocks
the path between X and Z (to avoid looping) and, therefore, destroys the VLAN setup
(because VLAN B needs these ports to receive messages).
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