Spanning-tree portfast is very easy to configure. Lets recap what it does
1. This should be configured on edge ports if configured on trunk ports connected between switches create loops.
2. Switches connected to server via trunk can be configured as "spanning-tree portfast trunk"
3. portfast enable ports skip listening and learning stages of STP
4. portfast enable ports does not generate TCN which in turn does not flush mac table.
5. This feature can also be enabled with BPDUfilter and BPDUguard.
R1(Fa0/0)-----SW1(Fa0/0)
SW1's Fa0/0 configured with "spanning-tree portfast"
Once R1 starts sending BPDU's SW1 disables the portfast from its interface connected to R1. However after sometime when R1 stops sending BPDUs, SW1 never automatically converts portfast state from disable to enable on the same interface
