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

Spanning Tree on JNCIS-ENT covers RSTP, MSTP, VSTP, and BPDU protection on Juniper EX Series switches. Questions test port roles and states, bridge priority defaults, MSTP instance 0 (CIST) behavior, edge port configuration, and loop-prevention reactions when BPDUs stop arriving.

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.

Editorial oversight:Johnson Ajibi· MSc IT Security, IEEE Senior Member

20 questionsDomain: Spanning Tree

Practice 10 questions Browse domain →

What the exam tests

What to know about Spanning Tree

Be able to identify RSTP port roles and states, explain MSTP instance 0 (CIST) behavior, recall the default bridge priority on EX Series switches, and describe why edge ports are configured on access ports. The key is knowing how a port reacts when BPDUs stop arriving.

RSTP port roles and states, including designated, root, alternate, and discarding transitions

MSTP instance 0 (CIST) operation and how it maps VLANs across regions

Default bridge priority on Juniper EX Series switches when RSTP is enabled

Edge port configuration on access ports and its effect on convergence and topology changes

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

▸Confusing RSTP alternate and backup port roles, or assuming a port that stops receiving BPDUs always becomes root.
▸Forgetting that MSTP instance 0 is the CIST and carries all VLANs not explicitly mapped to another instance.
▸Assuming edge ports still participate in spanning tree; they do not generate topology changes but still guard against loops.

Practice set

Spanning Tree questions

20 questions · select your answer, then reveal the explanation

Question 1easymultiple choice

Open the full VLAN trunking answer →

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

Trap 1: show spanning-tree statistics

This command displays packet statistics and BPDU counters.

Trap 2: show spanning-treemstp region

Used for MSTP regions, not basic RSTP global parameters.

Trap 3: show spanning-tree interface detail

Provides per-interface parameters rather than summary bridge/root parameters.

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

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

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?

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?

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?

Which RSTP port role replaces the legacy STP blocking and listening port states to provide rapid convergence?

Which command allows you to verify whether a specific interface on an EX Series switch is operating as an edge port?

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

Which command is used to display comprehensive spanning tree status, including port roles, states, and priorities across all interfaces on an EX Series switch?

You are troubleshooting an RSTP topology where a port remains in the discarding state. You suspect a proposal-agreement handshake is failing. Which mechanism is responsible for accelerating this handshake in RSTP?

You notice that an EX Series switch is experiencing frequent topology changes, causing intermittent packet drops across VLANs. Which command helps identify which specific interface is generating the topology changes?

An administrator implements MSTP and wants to configure a maximum hop count of 20 for instance 1. Which configuration command is used in Junos OS?

You need to verify the regional configuration name and revision number currently active on an EX Series switch running MSTP. Which operational command should you use?

Which TWO actions occur when you configure an interface as an edge port in RSTP? (Choose two.)

Which THREE parameters can be configured manually to influence root bridge selection in an RSTP network? (Choose three.)

Which TWO statements are true regarding loop protection in RSTP? (Choose two.)

Which TWO conditions will cause an MSTP boundary port to drop BPDUs or recognize a region separation? (Choose two.)

Which TWO parameters are typically configured when tuning RSTP timers on Junos EX Series switches? (Choose two.)

Which TWO operational commands are useful for troubleshooting MSTP configuration mismatches and instance status on Junos switches? (Choose two.)

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Frequently asked questions

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Study resources

Exam traps to avoid