Implementing the Rapid Spanning Tree Protocol – RSTP
What are edge ports?

An RSTP edge port is a switch port that is never intended to be connected to another switch device. It immediately transitioned to the forwarding state when enabled.

The edge port concept is well known to Cisco spanning tree users as it corresponds to the PortFast feature. All ports directly connected to end stations anticipate no switch device connected to them, immediately transition to the STP forwarding state thereby skipping the time consuming listening and learning stages. Neither edge ports nor PortFast enabled ports generate topology changes when the port transitions to a disabled or enabled status.

Unlike PortFast, an edge port that receives a BPDU immediately looses its edge port status and becomes a normal spanning tree port. A switch with the edge port receiving a BPDU generates a Topology Change Notification (TCN).

Cisco’s RSTP implementation maintains the PortFast keyword for edge port configuration, thus making an overall network transition to RSTP more seamless. Configuring an edge port where the port will be attached to another switch can have negative implications for RSTP when it is in the "sync" state.