Scenario practice questions

An administrator suspects that an interface is flapping but the router is remote and the connection is intermittent. The administrator wants to monitor the interface status without maintaining an SSH session. Which approach should be used?

Trap 1: Use 'monitor interface ge-0/0/0' and rely on terminal persistence

Terminal persistence is unreliable for intermittent connections.

Trap 2: Use 'monitor start' to capture logs

Still requires an active SSH session to receive the output.

Trap 3: Schedule a cron job to run 'show interfaces ge-0/0/0' every minute…

Requires SSH access and may miss events between polls.

A
Configure event-options to trigger on interface down and send syslog
Logs events remotely without requiring an active SSH session.
B
Use 'monitor interface ge-0/0/0' and rely on terminal persistence
Why wrong: Terminal persistence is unreliable for intermittent connections.
C
Use 'monitor start' to capture logs
Why wrong: Still requires an active SSH session to receive the output.
D
Schedule a cron job to run 'show interfaces ge-0/0/0' every minute and log output
Why wrong: Requires SSH access and may miss events between polls.

Open the full STP breakdown →

Question 2hardmultiple choice

An engineer enables Spanning Tree PortFast on a switch port connected to a host. Later, another switch is connected to that same port, causing a loop. What feature could have prevented this?

Trap 1: Loop guard

Loop guard prevents alternate ports from becoming designated in case of BPDU loss.

Trap 2: Root guard

Root guard prevents a port from becoming a root port, but does not stop BPDUs.

Trap 3: UplinkFast

UplinkFast is a Cisco proprietary feature for fast convergence.

A
Loop guard
Why wrong: Loop guard prevents alternate ports from becoming designated in case of BPDU loss.
B
BPDU guard
BPDU guard disables the port upon receiving a BPDU, preventing loops on PortFast ports.
C
Root guard
Why wrong: Root guard prevents a port from becoming a root port, but does not stop BPDUs.
D
UplinkFast
Why wrong: UplinkFast is a Cisco proprietary feature for fast convergence.

Question 3mediummultiple choice

A Juniper MX router is configured with multiple routing instances. In which scenario would an interface be automatically placed in a routing instance?

Trap 1: When the interface is configured with an IP address from the…

An interface is not automatically placed into an instance based on IP address; configuration is required.

Trap 2: When the interface is associated with the default instance.

The default instance is master, but this is not automatic for other instances.

Trap 3: When the routing instance type is virtual-router and the interface…

Even with virtual-router type, interfaces must be explicitly added.

A
When the interface is configured with an IP address from the instance's address family.
Why wrong: An interface is not automatically placed into an instance based on IP address; configuration is required.
B
When the interface is associated with the default instance.
Why wrong: The default instance is master, but this is not automatic for other instances.
C
When the interface is configured under the instance's `interface` statement.
Interfaces must be explicitly added to a routing instance using the `interface` command.
D
When the routing instance type is virtual-router and the interface is a physical interface.
Why wrong: Even with virtual-router type, interfaces must be explicitly added.

Question 4hardmultiple choice

A company has two Juniper routers in a high-availability cluster with dual Routing Engines. The administrator performs a commit on the primary RE. What is the effect of using the 'commit synchronize' command?

Trap 1: It performs a commit check on both REs but does not activate the…

It activates the config on both.

Trap 2: It commits the configuration only on the primary RE.

That would be a normal 'commit' without synchronize.

Trap 3: It commits the configuration only on the backup RE.

The primary is also committed.

A
It performs a commit check on both REs but does not activate the config.
Why wrong: It activates the config on both.
B
It commits the configuration on both Routing Engines simultaneously.
Synchronizes the commit to the backup RE.
C
It commits the configuration only on the primary RE.
Why wrong: That would be a normal 'commit' without synchronize.
D
It commits the configuration only on the backup RE.
Why wrong: The primary is also committed.

Read the full VPN explanation →

Question 5mediummultiple choice

Scenario: Your company has a Juniper SRX300 firewall used as a branch gateway. It runs Junos 15.1X49. The firewall has multiple security policies, NAT rules, and VPN tunnels. Recently, you added a new security policy to allow traffic from the internal network to a specific public server. After committing, you notice that the firewall is logging repeated denials for traffic that should be matched by the new policy. The policy appears correctly configured in the candidate configuration. You want to verify that the policy is actually active and check for any hidden rules that might be causing the issue. Which of the following is the most effective first step to troubleshoot this problem?

Trap 1: Roll back to the previous configuration to ensure the device is in…

Rolling back may remove the new policy and not address the root cause of ordering.

Trap 2: Run 'show configuration | display set | match policy' to verify the…

This shows the candidate configuration but not the active order; it may not reveal if another policy intercepts the traffic.

Trap 3: Check the firewall logs with 'show log messages | match deny' to…

Logs show denials but require interpretation; checking policy order is more direct.

A
Roll back to the previous configuration to ensure the device is in a known state.
Why wrong: Rolling back may remove the new policy and not address the root cause of ordering.
B
Run 'show configuration | display set | match policy' to verify the policy is present.
Why wrong: This shows the candidate configuration but not the active order; it may not reveal if another policy intercepts the traffic.
C
Run 'show security policies detail' and examine the policy order to see if a previous policy is denying the traffic.
This command displays all active security policies in sequence, helping identify ordering issues.
D
Check the firewall logs with 'show log messages | match deny' to see which policy is denying.
Why wrong: Logs show denials but require interpretation; checking policy order is more direct.

Read the full Scenario explanation →

Question 6mediummultiple choice

An engineer wants to roll back to the previous configuration without losing the current candidate changes. Which command should be used?

Trap 1: delete

C removes specific statements, not rollback.

Trap 2: rollback 0

B reverts to most recent commit.

Trap 3: commit check

D validates configuration, no change.

A
rollback 1
A discards candidate and reverts to previous commit.
B
delete
Why wrong: C removes specific statements, not rollback.
C
rollback 0
Why wrong: B reverts to most recent commit.
D
commit check
Why wrong: D validates configuration, no change.

Question 7mediummultiple choice

An administrator wants to ensure that if a network interface fails, the routing protocol process automatically restarts. Which Junos feature should be configured?

Trap 1: Nonstop Routing (NSR)

NSR provides hitless failover but not automatic process restart.

Trap 2: Bidirectional Forwarding Detection (BFD)

BFD detects failures quickly but does not restart processes.

Trap 3: Graceful Restart

Graceful restart helps maintain routing during a restart but does not automatically restart the process.

A
auto-restart
The 'auto-restart' configuration under routing options automatically restarts the routing protocol process if it fails.
B
Nonstop Routing (NSR)
Why wrong: NSR provides hitless failover but not automatic process restart.
C
Bidirectional Forwarding Detection (BFD)
Why wrong: BFD detects failures quickly but does not restart processes.
D
Graceful Restart
Why wrong: Graceful restart helps maintain routing during a restart but does not automatically restart the process.

Review the full OSPF breakdown →

Question 8easymultiple choice

You are a network engineer for a company that uses two Juniper routers, R1 and R2, connected via an Ethernet link. R1 and R2 are running OSPF in the same area, and R2 also has an eBGP session with a service provider to reach the internet. On R1, you have configured a static route to the subnet 172.16.10.0/24 with a next-hop of 192.168.1.2, which is the IP address of R2's interface facing R1. You have verified that the static route is configured correctly in the configuration, but traffic from R1 to 172.16.10.0/24 is not being forwarded. You check the routing table on R1 and see that the static route is present but marked as 'hidden'. You also notice that R1 has an OSPF-learned route to 192.168.1.0/30 (the link between R1 and R2) with a cost of 1. What is the most likely reason for the hidden static route?

Trap 1: Disable the eBGP session on R2 to remove the BGP routes from the…

Incorrect: BGP routes on R2 do not affect R1's static route next-hop reachability; the issue is on R1.

Trap 2: Increase the static route's preference to a lower value (e.g., 4).

Incorrect: the default preference of 5 is already very low; a lower preference would not help because the route is hidden, not competing with another route.

Trap 3: Configure a more specific static route to 172.16.10.0/24 with a…

Incorrect: a more specific route would still have the same next-hop and would also be hidden if the next-hop is unreachable.

A
Disable the eBGP session on R2 to remove the BGP routes from the routing table.
Why wrong: Incorrect: BGP routes on R2 do not affect R1's static route next-hop reachability; the issue is on R1.
B
Increase the static route's preference to a lower value (e.g., 4).
Why wrong: Incorrect: the default preference of 5 is already very low; a lower preference would not help because the route is hidden, not competing with another route.
C
Configure a more specific static route to 172.16.10.0/24 with a mask of /25.
Why wrong: Incorrect: a more specific route would still have the same next-hop and would also be hidden if the next-hop is unreachable.
D
Check if the next-hop IP 192.168.1.2 is reachable via the directly connected interface.
Correct: the next-hop unreachability is the most common cause of a hidden static route; verifying reachability (e.g., ping, ARP) will identify the issue.

Review the full OSPF breakdown →

Question 9hardmultiple choice

Scenario: Your company has a Juniper MX Series router at a branch office running Junos 18.4. The device has been in production for two years with a stable configuration. Yesterday, a senior engineer made several changes to the OSPF configuration to optimize routing for a new link. They committed the changes and left for the day. This morning, the branch office experiences intermittent connectivity, and the OSPF neighbor relationships are flapping. You suspect the recent OSPF changes caused the issue. You have remote console access to the router. The goal is to restore network stability as quickly as possible while preserving the ability to re-apply the changes after troubleshooting. Which course of action should you take?

Trap 1: Use 'deactivate protocols ospf' to disable OSPF entirely and then…

Deactivating all OSPF may stop routing completely, and piecemeal re-enablement is risky.

Trap 2: Immediately delete the OSPF configuration sections that were…

Manual re-entry is error-prone and time-consuming, prolonging the outage.

Trap 3: Perform a 'load factory-default' and 'commit' to reset the device…

Factory reset would wipe everything and require full reconfiguration, causing longer downtime.

A
Use 'deactivate protocols ospf' to disable OSPF entirely and then manually re-enable pieces.
Why wrong: Deactivating all OSPF may stop routing completely, and piecemeal re-enablement is risky.
B
Immediately delete the OSPF configuration sections that were changed and re-add the original settings manually.
Why wrong: Manual re-entry is error-prone and time-consuming, prolonging the outage.
C
Use 'rollback 1' to revert to the configuration before the changes, then 'commit confirmed 10' to verify stability.
Rollback to the previous commit (1) and commit confirmed provides quick restoration with safety.
D
Perform a 'load factory-default' and 'commit' to reset the device to base settings, then reconfigure from backup.
Why wrong: Factory reset would wipe everything and require full reconfiguration, causing longer downtime.