Bpdu Format - Huawei AR530 series Configuration Manual

Huawei AR530&AR550 Series Industrial Switch Routers
Configuration Guide - Ethernet Switching
Table 6-6 Values of STP parameters (in centiseconds)
Parameter
Hello Time
Max Age
Forward Delay

6.2.3 BPDU Format

The BID, root path cost, and PID are all carried in BPDUs. There are two types of STP BPDUs:
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A BPDU is encapsulated in an Ethernet frame. Its destination MAC address is a multicast MAC
address 01-80-C2-00-00-00.
Configuration BPDU
Configuration BPDUs are used most commonly.
Each bridge actively sends configuration BPDUs during initialization. After the network
topology becomes stable, only the root bridge actively sends configuration BPDUs. Other
bridges send configuration BPDUs only after receiving configuration BPDUs from upstream
devices. A configuration BPDU is at least 35 bytes long, including the parameters such as the
BID, root path cost, and PID. A bridge processes a received configuration BPDU only when it
finds that at least one of the sender BID and PID is different from that on the local receive port.
If both fields are the same as those on the receive port, the bridge drops the configuration BPDU.
In this way, the bridge does not need to process BPDUs with the same information as the local
port.
A configuration BPDU is generated in one of the following scenarios:
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Table 6-7
Issue 01 (2014-11-30)
Configuration BPDUs are heartbeat packets. STP-enabled designated ports send
configuration BPDUs at Hello intervals.
Topology Change Notification (TCN) BPDUs are sent only after a device detects a network
topology change.
After STP is enabled on ports of a device, the designated port on the device sends
configuration BPDUs at Hello intervals.
When the root port on a device receives a configuration BPDU, the device sends a copy of
the configuration BPDU to each of its designated ports.
When a designated port receives an inferior configuration BPDU, the designated port
immediately sends its own configuration BPDU to the downstream device.
describes fields in a BPDU.
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Default Value
200
2000
1500
6 STP/RSTP Configuration
Value Range
100-1000
600-4000
400-3000
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