PortFast

• PortFast doesnt disable STP on edge ports.
• Only put in blocked state
• Only send BPDU, doesnt recive BPDU
• Edge ports not subject to forward delay
• Not generate TCN (so no flush of CAM table, it cuts down the unknown unicast flooding in network) 
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• spanning-tree portfast default
• if enable portfast globally, every access port interfaces become portfast enabled port but not on trunk links
• some times there is a situation, enable portfast on trunk links also
• at that time use spanning-tree portfast trunk cmd used.
• If portfast enabled globally, when access port receive bpdu, it losses the portfast state and complete the listening & learning states then go to forwarding state
• But if portfast enable at interface level, port will remain in portfast state regardless of bpdu receive.
• show spanning-tree int e0/0 portfast