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5 Device Management
5.1 Ring Network
5.1.1 STP Definition
The protocol message adopted by STP is BPDU (Bridge Protocol Data Unit), which is also called
configuration information. BPDU contains enough information to ensure the calculation process of
spanning tree. STP can confirm network topological structure by transmitting BPDU among devices.
BPDU format and field description can realize the functions of spanning tree. Information is
interacted by transmitting BPDU message among switches. All the switches which support STP
protocol will receive and deal with the received message. The message carries all the useful
information in the data area which can be used for spanning tree calculation.
Figure 4-1 Frame format and field description of STP
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Protocol Identifier: The identification of protocol.
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Version: The protocol version.
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Message Type: BPDU type.
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Flag: Flag bit.
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Root ID: Root bridge ID, which is made up of 2-byte priority and 6-byte MAC address.
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Root Path Cost: The cost of root path.
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Bridge ID: The ID of bridge that sends BPDU, which is made up of 2-byte priority and 6-byte MAC
address.
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Port ID: Identifies the port that sends BPDU.
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Message Age: Life time of BPDU.
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Max Age: Aging time of current BPDU, also the longest time for port to save BPDU.
●
Hello Time: The period cycle of Bridge Root sending BPDU.
●
Forward Delay: The time of maintaining snoop and study status before sending data package,
after topology is changed.
5.1.2 Configuring STP Bridge
Step 1
Select
Device Management
>
Spanning Tree
>
STP Bridge Settings
on the
System Info
