CCNA 2.7.a: PortFast

Overview:

PortFast is a Spanning-Tree option that causes a port to immediately come up without going through initial STP learning and listening phases

 

Study Notes:

  • STP PortFast causes a Layer 2 LAN port configured as an access port to enter the forwarding state immediately, bypassing the listening and learning states
  • You can use PortFast on Layer 2 access ports connected to a single workstation or server to allow those devices to connect to the network immediately, instead of waiting for STP to converge
  • Interfaces connected to a single workstation or server should not receive bridge protocol data units (BPDUs)
  • When configured for PortFast, a port is still running the spanning tree protocol
  • A PortFast enabled port can immediately transition to the blocking state if necessary (this could happen on receipt of a superior BPDU)
  • PortFast can be enabled on trunk ports
  • PortFast can have an operational value that is different from the configured value
  • Beginning with Cisco IOS Release 12.2(33)SXI, PortFast options are edge and normal
  • There is no difference between edge ports and PortFast ports.
  • Caution: Because the purpose of PortFast is to minimize the time that access ports must wait for STP to converge, it should only be used on access (edge) ports. If you enable PortFast on a port connected to a switch (a network port), you might create a temporary bridging loop.

 

PacketTracer Lab: CCNA-2.7.a-How-to-configure-Portfast.pkt

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