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.