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QSW-2900-24T4-AC
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Qtech QSW-2900-24T4-AC [145/209] Figure 2 network diagram for stp algorithm

Qtech QSW-2900-24T-AC [145/209] Figure 2 network diagram for stp algorithm

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Step Description

3

The device compares the calculated configuration BPDU with the configuration BPDU

on the port of which the port role is to be defined, and does different things according to

the comparison result:

· If the calculated configuration BPDU is superior, the device will consider this

port as the designated port, and the configuration BPDU on the port will be

replaced with the calculated configuration BPDU, which will be sent out

periodically.

· If the configuration BPDU on the port is superior, the device will block this port

without updating its configuration BPDU, so that the port will only receive

BPDUs, but not send any, and will not forward data.

& Note:

When the network topology is stable, only the root port and designated ports forward traffic, while

other ports are all in the blocked state – they only receive STP packets but do not forward user traffic.

Once the root bridge, the root port on each non-root bridge and designated ports have been successfully

elected, the entire tree-shaped topology has been constructed.

The following is an example of how the STP algorithm works. The specific network diagram is shown in

Figure 2. In the feature, the priority of Device A is 0, the priority of Device B is 1, the priority of Device C is 2, and

the path costs of these links are 5, 10 and 4 respectively.

Figure 2 Network diagram for STP algorithm

· Initial state of each device

The following table shows the initial state of each device.

Table 4 Initial state of each device

Device Port name BPDU of port

AP1 {0, 0, 0, AP1}

Device A

AP2 {0, 0, 0, AP2}

BP1 {1, 0, 1, BP1}

Device B

BP2 {1, 0, 1, BP2}

CP1 {2, 0, 2, CP1}

Device C

CP2 {2, 0, 2, CP2}

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