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Why Is the Recommended Value of STP Network Radius Within 7?
According to the initial spanning tree protocol, the default interval for an STP switch to send BPDUs is 2 seconds. Each switch receives and processes BPDUs for about 1 second each time, and supports a maximum of 20 hops.
According to the RSTP protocol, packets are aged after three intervals (6 seconds) by default. If a hop takes 1 second, a packet times out after 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 the maintainability and manageability of the network.