Spanning tree portfast

Spanning-tree portfast command makes interface on the switch jump up from spanning-tree disable mode to spanning-tree forwarding mode which is different from the normal spanning tree operation that the interface needs to go through listening status and learning state. Therefore, the interface will come up right away.

How to enable spanning-tree portfast


Spanning-tree portfast in interface level
  In the interface level we use " spanning-tree portfast" command to enable it. This is for an access port only. If you want to enable portfast for trunk port "spanning-tree portfast trunk" is required.


Spanning-tree portfast option in the global configuration
  In the global configuration, we can enable the portfast for all of the access ports on the switch by using "spanning-tree portfast default " command. However, this command will not affect the trunk port on the switch

Option for spanning-tree portfast
   - spanning-tree portfast bpduguard default

   - spanning-tree portfast bpdufilter default

   -spanning-tree portfast bpduguard default :  it will enable the bgpuguard on the all of the portfast interfaces on the switch. This is only valid for access port.

   - spanning-tree portfast bpdufilter default  :  it will enable the bgpufilter on the all of the portfast interfaces on the switch. This is only valid for access port.

BPDU filter

BPDUs are the messages exchanged between switches to calculate the spanning tree topology. BPDU filter is a feature used to filter sending or receiving BPDUs on a switchport.

It is extremely useful on those ports which are configured as portfast ports as there is no need to send or receive any BPDU messages on of these ports.

BPDU filter can be configured globally or under the interface level. When configured globally all portfast enabled ports stop sending and receiving BPDUs, but if a BPDU is received on the port it gets out of the portfast state and normally participate in the spanning tree calculations.