Troubleshooting STP Flashcards
6 cards from real STP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Troubleshooting STP flashcards as text
What is Unidirectional Link Detection (UDLD)?
Answer: A protocol that detects one-way communication failures on fiber links that could cause STP loops
UDLD monitors bidirectional communication on links, shutting down ports where only one direction is working to prevent STP from making incorrect decisions.
What is the impact of incorrect STP timer modifications?
Answer: Can cause network instability, premature convergence failures, or delayed failover
Modifying STP timers without understanding the implications can cause ports to transition states too quickly (creating loops) or too slowly (causing unnecessary downtime).
How does STP handle a switch receiving superior BPDUs on its root port?
Answer: The switch updates its root bridge information and recalculates the spanning tree topology
When a switch receives a superior BPDU (from a bridge with a lower ID), it updates its understanding of the topology and may select a new root bridge and root port.
What is the purpose of STP path cost manipulation?
Answer: To influence which paths STP selects as primary forwarding paths by adjusting port costs
By adjusting port costs, network administrators can make STP prefer certain paths over others, optimizing traffic flow according to network design goals.
What happens when PortFast is incorrectly enabled on a switch-to-switch link?
Answer: It can cause temporary bridging loops because the port skips listening and learning states
Enabling PortFast on inter-switch links bypasses STP protection, potentially causing loops during topology changes since the port immediately forwards traffic.
How do you verify STP is functioning correctly on a network?
Answer: Check that one root bridge exists per VLAN, all ports are in expected states, and no topology changes are occurring unexpectedly
Verifying STP health involves confirming proper root bridge election, correct port roles and states, and monitoring for unexpected topology changes that could indicate problems.