Why is the recommended value of STP network radius within 7

According to the initial spanning tree protocol, the default interval for sending BPDUs is 2 seconds. It takes a switch about 1 second to receive and process BPDUs each time. An STP network can have a maximum of 20 hops.

According to the RSTP protocol, packets are aged after three intervals (6 seconds by default). If each hop spends 1 second for BPDU processing, a BPDU will time out after passing through 6 hops. Therefore, the recommended value of STP network radius cannot be greater than 7.

There are also some other considerations, such as bandwidth usage, storm range, and network maintainability and manageability.

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