A wastewater plant wants spanning tree to prefer a dark-fiber ring over a slower microwave backup without disabling loop protection. Which mechanism correctly biases the path?
Select an answer to reveal the explanation.
Short Explanation
STP cost is the toll on each bridge path—raise the toll on microwave and cars take the dark-fiber ring. You’re steering preference, not deleting loop protection. Leave both links in the topology; just make fiber the cheap road.
Full Explanation
Spanning Tree selects paths using root cost, so operators can raise the microwave uplink cost (or lower the fiber cost) to prefer the dark-fiber ring while keeping both links in the topology. That bias preserves loop prevention instead of shutting links or disabling STP. OSPF metrics do not drive STP decisions, and PortFast is inappropriate on redundant inter-switch uplinks. After the change, verify root placement and that microwave still provides a valid alternate on fiber failure.