STP bases its operation on several timers. Usually, the default timer values are used for proper STP behavior. The defaults are based on a network diameter of seven switches but can be adjusted for faster convergence times.
- The Hello Timer triggers periodic hello messages to neighboring switches.
- The Forward Delay timer specifies the time a port stays in each of the listening and learning states.
- The MaxAge timer specifies the lifetime of a stored BPDU received on a designated port. After the timer expires, other ports can become designated ports.
BPDUs are expected at regular intervals. If they are delayed beyond the lapse of an STP timer, topology changes can be triggered in error. This condition can be detected ...