Forward time : Determines how long each of the listening and learning states last before the port begins forwarding. Switch(config)# [ no ] spanning-tree vlan vlan_ID forward-time forward_timeConfigures the forward time of a VLAN. The forward_time value can be from 4 to 30 seconds. https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst4500/12-2/15-02SG/configuration/guide/config/span