Match each STP or switch protection feature to the problem it is mainly designed to prevent.
Drag a concept onto its matching description — or click a concept then click the description.
Reduces delay for an end-host access port to reach forwarding
Err-disables a PortFast port that unexpectedly receives a BPDU
Prevents an access or designated port from becoming a new root port because of superior BPDUs
Helps stop a non-designated port from transitioning to forwarding when BPDUs stop arriving
⚠ Common exam trap
The exam trap is confusing BPDU Guard with Root Guard or Loop Guard. Remember that BPDU Guard specifically protects against rogue switches by shutting down the port if a BPDU is received on a PortFast port.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Root Guard: Prevents a switch from becoming root bridge due to rogue BPDUs
STP protection features prevent specific problems: Root Guard protects root bridge election, BPDU Guard prevents loops on access ports, Loop Guard handles BPDU loss, UDLD detects unidirectional links, and PortFast speeds up port transition.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Root Guard: Prevents a switch from becoming root bridge due to rogue BPDUs
Why this is correct
Root Guard enforces the location of the root bridge by monitoring designated ports for superior BPDUs. When a port receives a BPDU that would make the attached switch the root, the port is moved to a root-inconsistent state, blocking traffic without shutting down. This prevents an attacker or misconfigured switch from hijacking the spanning-tree topology.
BPDU Guard: Prevents loops by disabling ports that receive BPDUs on access ports
Why this is correct
BPDU Guard provides protection on access ports by immediately disabling any port that receives a BPDU, which indicates an unauthorized switch or bridge connection. The port is placed into errdisable state, effectively cutting off the potential loop source. This is a proactive measure that stops loops at the edge of the network.
Loop Guard: Prevents alternate/root ports from becoming designated due to BPDU loss
Why this is correct
Loop Guard addresses the failure mode where a port in alternate or root role stops receiving BPDUs due to a unidirectional link or software malfunction. Instead of transitioning to designated and forwarding, the port is placed into loop-inconsistent state, maintaining the blocking role. This prevents an STP loop where a switch incorrectly assumes it is the root.
UDLD: Detects unidirectional links to prevent loops
Why this is correct
UDLD, or Unidirectional Link Detection, works at Layer 2 to identify fiber or copper links where traffic is transmitted in only one direction. When a unidirectional link is detected, the port is shut down, preventing the forwarding of traffic that could create a loop invisible to STP. This complements STP by physically inspecting link health.
Visual reference
Go deeper
Learn chapter
Configuring Switch Ports for Desktops, VoIP Phones, APs, IoT, and Virtualized Hosts
Key term
Root bridge
The root bridge is the central reference point in a Spanning Tree Protocol (STP) network, serving as the logical root of the spanning tree topology.
Key term
STP
STP (Spanning Tree Protocol) is a network protocol that prevents loops in Ethernet networks by creating a loop-free logical topology.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-301 exam.