JN0-106 Practice Test 13 — 15 Questions

Question 1

What is the purpose of the 'commit confirmed' command in Junos OS?

Accepted Answer

It allows the administrator to test a configuration change with automatic rollback if confirmation is not received. The 'commit confirmed' command in Junos OS applies a candidate configuration change and starts a confirmation timer (default 10 minutes). If the administrator does not issue a 'commit' command before the timer expires, the system automatically rolls back to the previous active configuration. This allows safe testing of changes, especially over remote connections, preventing lockout if the change breaks connectivity.

Answer

It compares the candidate configuration with the active configuration

Answer

It permanently saves the candidate configuration to the startup configuration

Answer

It confirms that a previous commit was successful

Question 2

An engineer is troubleshooting a network issue where hosts on the same VLAN cannot communicate with each other. Which configuration element is most likely missing?

Accepted Answer

Spanning Tree Protocol enabled. Hosts on the same VLAN communicate at Layer 2 and do not require any Layer 3 configuration such as an IRB interface or default gateway. The most likely missing configuration is that Spanning Tree Protocol (STP) is not enabled. Without STP, loops can cause broadcast storms and MAC address flapping, preventing communication between hosts in the same VLAN. Therefore, option A is correct.

Answer

An IRB interface for the VLAN

Answer

A Layer 3 switchport

Answer

A default gateway for the VLAN

Question 3

Order the steps to configure firewall filters (ACLs) in Junos.

Accepted Answer

First configure match conditions, then configure the action, and finally apply the filter to the interface.. Firewall filters are defined with terms (match conditions and actions) and applied to interfaces.

Answer

First apply the filter to the interface, then configure match conditions, then configure the action.

Answer

First configure the action, then configure match conditions, then apply the filter to the interface.

Answer

First configure match conditions, then apply the filter to the interface, then configure the action.

Question 4

You are a network engineer for a large enterprise deploying a new data center using a spine-and-leaf architecture with Juniper QFX5100 switches. The underlay network uses OSPF for loopback reachability, and the overlay uses EBGP for EVPN. The leaf switches are configured as VTEPs (Virtual Tunnel Endpoints). One of the leaf switches, leaf-03, cannot establish OSPF adjacency with its spine switch, spine-01. The interfaces are up/up and the IP addresses are correctly configured. 'show ospf neighbor' on leaf-03 returns nothing. 'show ospf interface' shows the interface is in state DOWN. Both switches are configured with the same OSPF area (0.0.0.0) and the same hello interval (10 seconds). The MTU on both sides is 1500. Authentication is not configured. The spine switch has multiple OSPF neighbors from other leaves. The network is in production and other leaf switches are working fine. What is the most likely cause of the problem?

Accepted Answer

OSPF is disabled on the interface at the leaf switch.. The OSPF interface is in state DOWN while the physical interface is up/up, indicating that OSPF is not enabled on that interface. This can happen if OSPF is explicitly disabled under protocol configuration or if the interface is not included in the OSPF configuration. Option A is wrong because network type mismatch would not cause the interface state to be DOWN; adjacency would fail but the interface would remain UP. Option B is wrong because MTU issues would cause OSPF adjacency problems but the interface state would be UP (not DOWN). Option D is wrong because duplicate router IDs would affect all adjacencies, not just this one, and other leaves are working fine.

Answer

The OSPF network type is not consistent between the two switches.

Answer

The interface MTU is misconfigured on one side.

Answer

Duplicate router ID on leaf-03 and spine-01.

Question 5

A technician notices that the /var partition is filling up on a Juniper device. Which action would be most appropriate to free up space while preserving critical logs?

Accepted Answer

Run 'request system storage cleanup'. The 'request system storage cleanup' command is the correct action because it safely removes non-essential files such as old log files, core dumps, and temporary files that are no longer needed, while preserving critical logs and configuration files. This command performs a controlled cleanup without risking the deletion of important operational data, making it the most appropriate method for freeing up space on the /var partition.

Answer

Delete core files manually

Answer

Reboot the device

Answer

Delete all files in /var/log

Question 6

Which THREE statements about the 'commit' command are correct?

Accepted Answer

The 'commit check' command validates the syntax of the candidate configuration.. The 'commit check' command validates the syntax and semantics of the candidate configuration without activating it. This allows an administrator to verify that the configuration is valid before committing, preventing potential errors from being applied to the active configuration.

Answer

The 'commit full' command activates the configuration without performing any validation.

Answer

The 'commit' command can only be issued when no other users are in configuration mode.

Question 7

Refer to the exhibit. If the primary next-hop (192.168.1.1) becomes unreachable, what will happen to the route?

Accepted Answer

The secondary next-hop (192.168.2.1) will be used.. In Junos, when a route has multiple next-hops configured (e.g., primary and secondary), the secondary next-hop serves as a backup. If the primary next-hop (192.168.1.1) becomes unreachable, Junos automatically fails over to the secondary next-hop (192.168.2.1) without removing the route from the routing table. This behavior is controlled by the 'next-hop' configuration under a static route or via routing protocol policies, ensuring continuous reachability.

Answer

The route is removed from the routing table.

Answer

The route remains but with the primary next-hop marked as unreachable.

Answer

The route becomes hidden.

Question 8

An engineer wants to roll back to the previous configuration. Which command should be used?

Accepted Answer

rollback 1. The `rollback 1` command loads the previous committed configuration (the configuration before the last commit) into the candidate configuration, discarding any uncommitted changes. This allows the engineer to replace the current candidate with the desired historical configuration. In Junos, `rollback 0` loads the most recently committed configuration (the current active configuration), not the previous one.

Answer

delete

Answer

rollback 0

Answer

commit check

Question 9

An organization has two ISPs and wants to load-balance traffic equally across both links for all outbound traffic. Which routing configuration approach should be used?

Accepted Answer

Configure two static default routes with equal metric values and enable ECMP.. Configuring two static default routes with equal metric values and enabling Equal-Cost Multi-Path (ECMP) allows the Juniper device to load-balance outbound traffic equally across both ISP links. ECMP uses per-flow or per-packet load balancing based on the hash of source/destination IP addresses and ports, ensuring traffic is distributed evenly without relying on dynamic routing protocols.

Answer

Configure two static default routes with different metric values.

Answer

Configure policy-based routing to match all traffic and forward to both ISPs.

Answer

Establish BGP sessions with both ISPs and rely on BGP path selection.

Question 10

You are a network engineer for a company that has just deployed a Juniper SRX firewall in a branch office. The device has multiple interfaces: ge-0/0/0 connected to the internet, ge-0/0/1 connected to the internal LAN (192.168.1.0/24), and ge-0/0/2 connected to a DMZ (10.0.0.0/24). After initial configuration, you attempt to ping from the SRX to a server on the internet (8.8.8.8) but receive no response. You also notice that internal users can access the internet. You have verified the routing table shows a default route via ge-0/0/0. The security policies appear correct. You suspect the issue is related to interface configuration. What is the most likely cause and the correct course of action?

Accepted Answer

The interface ge-0/0/0 is missing the 'host-inbound-traffic' configuration under its security zone; you should add the appropriate system services under the zone.. The SRX can ping internal hosts but not the internet because the interface ge-0/0/0 is in the untrust zone, which by default blocks all inbound traffic, including pings originated from the device itself. The 'host-inbound-traffic' configuration under the security zone allows system services such as ping, SSH, and SNMP to be received on that interface. Without it, even though the routing table and security policies are correct, the SRX will drop its own outbound ICMP echo requests before they can be sent, or drop the replies if they are treated as inbound traffic.

Answer

The security policy from the trust zone to the untrust zone is blocking traffic; you should create a policy allowing all traffic from the SRX itself.

Answer

The interface ge-0/0/0 has an incorrect MAC address; you should clear the ARP cache.

Answer

The default route is missing or incorrect; you should add a default route via the internet gateway IP.

Question 11

Which TWO commands can be used to view the current running configuration?

Accepted Answer

show configuration | display set. The 'show configuration | display set' command outputs the current active configuration in 'set' format, which is a flat, line-by-line representation of configuration statements. Option D is correct because 'show configuration' without any pipe modifier displays the entire running configuration in its native hierarchical format. Both commands allow you to view the current running configuration, just in different presentation styles.

Answer

show configuration | display inheritance

Answer

show configuration | match

Answer

show configuration | compare

Question 12

Refer to the exhibit. What is the most likely cause of this BGP route being hidden?

Accepted Answer

The next-hop 192.168.100.1 is not reachable via any active route.. In JUNOS, a BGP route is hidden when the next-hop address is not reachable via any active route in the routing table. The show route protocol bgp command displays the route as hidden if the next-hop 192.168.100.1 is not resolvable, because BGP requires a valid IGP or static route to the next-hop for the route to be considered active and installed in the forwarding table.

Answer

The route has a higher preference than another route.

Answer

The BGP session to 10.0.0.2 is down.

Answer

The prefix 10.1.1.0/24 is filtered by an import policy.

Question 13

A network administrator configures a static route on a Juniper device: `set routing-options static route 192.168.100.0/24 next-hop 10.0.0.1`. The administrator verifies the route is present in the routing table but notices it is not active. What is the most likely cause?

Accepted Answer

The next-hop address 10.0.0.1 is not reachable.. A static route becomes active only if the next-hop address is reachable via a directly connected or active route in the routing table. Since the administrator verified the route is present but not active, the most likely cause is that the next-hop 10.0.0.1 is not reachable (e.g., no ARP resolution or no interface with that subnet). Junos marks such routes as hidden or inactive until the next hop is reachable.

Answer

The route is not committed.

Answer

The preference of the static route is higher than 15.

Answer

The destination prefix is already learned via OSPF with a lower metric.

Question 14

A network engineer made several configuration changes on a Juniper QFX switch to implement new VLANs. After committing the changes, the engineer realized that the new configuration caused a critical loss of connectivity to the management network. The engineer needs to revert to the previous configuration that was working. The switch is still accessible via the console port, and the engineer has privilege level access. The previous configuration was committed two commits ago, and the current active configuration is the problematic one. Which action should the engineer take to restore the previous working configuration?

Accepted Answer

Execute 'rollback 2' followed by 'commit'.. The working configuration was committed two commits ago. The 'rollback 2' command loads the configuration from two commits prior into the candidate configuration. After that, 'commit' makes it active, restoring connectivity. Note that 'rollback 1' would load the intermediate commit, which is also problematic, and 'rollback 0' refers to the current active configuration.

Answer

Use 'load override /config/juniper.conf.1.gz' followed by 'commit'.

Answer

Use 'delete system' to remove all configuration and then commit.

Answer

Execute 'rollback 0' followed by 'commit'.

Question 15

A Juniper device fails to boot and stops at the 'loader>' prompt. What is the most likely cause of this issue?

Accepted Answer

Bad boot device or missing kernel. When a Juniper device stops at the 'loader>' prompt, it indicates that the boot process has failed to locate or load the kernel (juniper-kernel) from the boot device (e.g., internal flash, USB, or hard disk). This is typically caused by a corrupted boot device, missing kernel image, or incorrect boot device selection in the boot loader (UBoot or CFE). The loader prompt is a low-level environment used for recovery, not a sign of configuration or authentication issues.

Answer

Corrupted configuration file

Answer

Hardware failure of the power supply

Answer

Missing root password