Calculating and Using Forward Delay

The entire pre-forwarding period can be calculated by combining these four parts:


= end-to-end_bpdu_propagation_delay + message_age_overestimate + tx_halt_delay + max_frame_lifetime = 14 + 6 + 1 + 8 = 29 seconds

Because the pre-forwarding period is divided into two halves, this number can be divided by two to calculate Forward Delay:


As with Max Age, you can substitute the appropriate values for your network to potentially calculate a smaller Forward Delay value (only modify diameter and Hello Time). This value can then be set on Root Bridges using the following command:

set spantree fwddelay delay [vlan]

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