KYLAND Technology SICOM3024P, Web Operation Manual

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Advanced Configuration
94
the received one.
Devices compare the BPDUs of all ports and figure out the best BPDU. Principles for
comparing BPDUs are as follows:

The BPDU with a smaller root bridge ID has a higher priority.

If the root bridge IDs of two BPDUs are the same, their root path costs are compared. If
the root path cost in a BPDU plus the path cost of the local port is smaller, then the priority
of the BPDU is higher.

If the root path costs of two BPDUs are also the same, the designated bridge IDs,
designated port IDs, and IDs of the port receiving the BPDUs are further compared in
order. The BPDU with a smaller ID has a higher priority. The BPDU with a smaller root
bridge ID has a higher priority.
3. Selection of the root bridge: The root bridge of the spanning tree is the bridge with the
smallest bridge ID.
4. Selection of the root port: A non-root-bridge device selects the port receiving the best
BPDU as the root port.
5. BPDU calculation of the designated port: Based on the BPDU of the root port and the path
cost of the root port, a device calculates a designated port BPDU for each port as follows:

Replace the root bridge ID with the root bridge ID of the BPDU of the root port.

Replace the root path cost with the root path cost of the root port BPDU plus the path cost
of the root port.

Replace designated bridge ID with the ID of the local device.

Replace the designated port ID with the ID of the local port.
6. Selection of the designated port: If the calculated BPDU is better, then the device selects
the port as the designated port, replaces the port BPDU with the calculated BPDU, and
sends the calculated BPDU. If the port BPDU is better, then the device does not update
the port BPDU and blocks the port. Blocked ports can receive and forward only RSTP
packets, but not other packets.
6.13.5 Web Configuration
1. Enable STP/RSTP, as shown in the following figure.