Question

Which Cisco switch feature ensures that configured switch edge ports do not cause Layer 2 loops if a port is mistakenly connected to another switch?

A) spanning tree protocol (stp)
B) virtual local area network (vlan)
C) dynamic trunking protocol (dtp)
D) portfast

Answer 1

The Cisco switch feature designed to prevent Layer 2 loops on edge ports when mistakenly connected to another switch is PortFast. PortFast allows connected devices to bypass the usual STP states and go directly to forwarding, with BPDU Guard providing additional loop prevention.

Step-by-step explanation:

The Cisco switch feature that ensures configured switch edge ports do not cause Layer 2 loops if a port is mistakenly connected to another switch is PortFast. PortFast is a feature that can be enabled on switch ports connected to single hosts to skip the usual STP listening and learning states and proceed directly to the forwarding state. This feature is crucial in preventing temporary loops during the STP convergence time when devices like servers or workstations are starting up. However, if a port with PortFast enabled is connected to another switch, it could create network loops. To prevent this from accidentally happening, Cisco switches use a feature called BPDU Guard, which automatically disables the port if a BPDU is detected on that port, thus keeping the network protected from potential loops.