How should I use these Spanning Tree practice questions?

Read each scenario carefully and choose your answer before revealing the explanation. Then check why your choice was right or wrong. Repeat until the reasoning feels automatic.

Can I practise just Spanning Tree questions in a focused session?

Yes — use the session launcher on this page to start a 10-, 20-, 30- or 50-question session drawn entirely from the Spanning Tree domain.

JNCIS-ENT · topic practice

Spanning Tree practice questions

Practise JNCIS-ENT STP questions covering root bridge election, bridge IDs, port roles (root, designated, blocking), path cost, PortFast, BPDU Guard, and how spanning tree prevents Layer 2 loops.

Courseiva uses original exam-style practice questions designed for learning and revision. The goal is to understand the concepts, recognise exam patterns, and improve through explanations — not memorise copied exam dumps.

Reviewed byJohnson Ajibi· MSc IT Security

20 questionsDomain: Spanning Tree

Practice 10 questions Browse domain →

What the exam tests

What to know about Spanning Tree

STP questions usually test root bridge election, port roles, path cost and how spanning tree prevents Layer 2 loops.

Root bridge election and bridge ID comparison.

Root ports, designated ports and blocked/alternate ports.

Path cost and how switches choose the best path to the root bridge.

PortFast, BPDU Guard and common Layer 2 loop-prevention behaviour.

Why learners struggle

Why Spanning Tree questions are commonly missed

STP questions are missed when learners confuse bridge ID comparison direction, forget how ties are broken, or misidentify which port role a given switch port takes. The lowest bridge ID wins, but cost, port ID, and tiebreakers all play a role.

·Lowest bridge ID wins root election — lower priority wins, then lower MAC breaks ties
·Root port vs designated port — each non-root switch has exactly one root port
·Blocking ports are on non-designated segments — they receive BPDUs but do not forward
·PortFast bypasses STP states — only safe on access ports connected to end devices
·BPDU Guard shuts down PortFast ports that receive BPDUs — protecting against loops
·STP path cost uses link bandwidth — faster links have lower cost and are preferred

Watch out for

Common Spanning Tree exam traps

▸The lowest bridge ID wins root bridge election.
▸A non-root switch has one root port: its best path toward the root bridge.
▸PortFast should be used carefully on access ports, not normal switch-to-switch links.
▸Lower STP cost is preferred, but bridge ID and port ID can break ties.

Practice set

Spanning Tree questions

20 questions · select your answer, then reveal the explanation

Question 1hardmultiple choice

Open the full STP breakdown →

An administrator needs to configure MSTP on a group of EX Series switches. Which three parameters must be identical across all switches in the same MST region?

Trap 1: MAC address, system ID extension, and MSTP version

MAC addresses are unique per device, and MSTP version is standard.

Trap 2: Bridge priority, root identifier, and Hello timer

Bridge priority and timers can vary between switches within the same MST region.

Trap 3: Max age, forward delay, and region map digest

The digest is a mathematical result of the configuration name, revision, and VLAN mappings, not a manually configured parameter.

Spanning Tree practice questions

What to know about Spanning Tree

Why Spanning Tree questions are commonly missed

Common Spanning Tree exam traps

Spanning Tree questions

An administrator needs to configure MSTP on a group of EX Series switches. Which three parameters must be identical across all switches in the same MST region?

Which protocol standard defines Rapid Spanning Tree Protocol (RSTP)?

Which TWO conditions will cause an RSTP port configured with loop protection to transition into a discarding state? (Choose two.)

You are configuring Multiple Spanning Tree Protocol (MSTP) across multiple EX Series switches in your enterprise network. Which three parameters must be identical across all switches to ensure they belong to the same MST region?

Which TWO actions occur when you configure an interface as an edge port using 'set protocols rstp interface ge-0/0/10.0 edge' on a Juniper switch? (Choose two.)

When configuring and verifying MSTP on Junos devices, which THREE statements are correct regarding regional boundaries and communication? (Choose three.)

What is the default bridge priority value assigned to Juniper EX Series switches when RSTP is enabled?

Which command allows an operator to view the designated root bridge identifier and port roles for all active VLANs under RSTP?

You need to ensure that a core switch retains its position as the root bridge even if a new switch with a manually lowered bridge priority is added to the network. Which feature should you configure on the core switch's ports facing the downstream switches?

An EX Series switch running RSTP receives BPDUs with superior path cost information from an unauthorized access switch. Which feature should you enable on access-facing ports to prevent these unauthorized BPDUs from altering the spanning tree topology?

You are troubleshooting a suboptimal spanning tree topology where an EX4300 switch is chosen as the STP Root Bridge despite having a high bridge priority. What command helps verify the current bridge priority and local bridge identifier parameters?

While examining an RSTP topology, you notice that a designated port has suddenly stopped receiving BPDUs from its upstream neighbor, causing the port to transition into a discarding state to prevent potential loops. Which feature is actively providing this protection?

An administrator has deployed a new EX Series switch running RSTP and notices that access ports connected to end-user workstations take up to 30 seconds to transition to the forwarding state. Which configuration command should be applied to immediately resolve this delay for access ports?

What is the role of the Root Port in an RSTP topology?

An enterprise network runs MSTP. Instance 0 is always reserved for which specific purpose?

What is the primary function of the RSTP port role known as the 'Backup' port?

You are configuring MSTP and want to assign VLANs 10 through 50 to MST instance 2. Which configuration hierarchy is correct in Junos OS?

You suspect that a network loop has formed due to a misconfigured RSTP topology on your EX Series switches. Which command shows real-time topology change notifications and counts on the switch?

When configuring MSTP, what purpose does the regional configuration digest serve?

An operator configures RSTP across multiple EX Series switches. A rogue switch running legacy STP is connected to an RSTP switch. How does the RSTP switch handle interaction with the legacy STP switch?

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Frequently asked questions

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Study resources

Exam traps to avoid