JNCIA-JUNOS Practice Test 3 — 25 Questions

Question 1

Refer to the exhibit. An engineer has made changes to the candidate configuration. What will happen when the engineer issues the 'commit' command?

Accepted Answer

Both the interface address and security policy will be activated.. Option D is correct because in Junos, the 'commit' command activates all changes in the candidate configuration atomically. Both the interface address change and the security policy will be applied simultaneously after validation. Junos does not require a reboot for security policy changes, and syntax errors cause the commit to fail, not be ignored.

Answer

The commit will succeed but the security policy will be ignored due to a syntax error.

Answer

Only the interface address change will be committed because security policies require a reboot.

Answer

The configuration will be validated; if errors exist, the commit will fail.

Question 2

Refer to the exhibit. An engineer wants to verify that static routes for 10.0.1.0/24 and 10.0.2.0/24 are present in the routing table. Based on the output, which statement is true?

Accepted Answer

Both routes are active and have the same preference value.. The output shows both 10.0.1.0/24 and 10.0.2.0/24 as static routes with a preference of 5. Since the preference value is the same and both are listed as active (the 'A' flag is present in the routing table), both routes are installed and active in the forwarding table. In Junos, a static route's default preference is 5, and any route with a lower preference is preferred; here both have equal preference, so they coexist as active routes.

Answer

Both routes have a preference of 0.

Answer

Only the 10.0.1.0/24 route is active.

Answer

Both routes use the same next-hop IP address.

Question 3

Refer to the exhibit. How many static default routes are configured?

Accepted Answer

2. Option D is correct because the exhibit shows two static routes with a next-hop of 0.0.0.0, which are static default routes. In JUNOS, a static default route is defined by a destination prefix of 0.0.0.0/0 (or ::/0 for IPv6). The configuration lists two such routes, each with a different next-hop address, confirming two static default routes.

Answer

1

Answer

0

Answer

3

Question 4

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.. Option C is correct because 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 5

When configuring a new Juniper router, an engineer needs to ensure that configuration changes are not automatically committed after a certain time if not explicitly confirmed. Which configuration parameter controls this?

Accepted Answer

commit confirmed. The 'commit confirmed' command is used to apply a configuration change that will automatically roll back to the previous configuration if not explicitly confirmed within a specified time period (default 10 minutes). This ensures that changes are not permanently applied unless the engineer verifies them, preventing accidental lockout or misconfiguration.

Answer

commit check

Answer

commit at

Answer

commit synchronize

Question 6

Which TWO statements are true regarding the Junos OS commit model?

Accepted Answer

Multiple users can make changes simultaneously in configure private mode.. Option C is correct because Junos OS allows multiple users to enter configure private mode, where each user has an independent candidate configuration. This prevents conflicts and allows simultaneous edits without interfering with each other's changes. Option E is correct because the 'commit' command activates the candidate configuration, making it the active configuration on the device.

Answer

Configuration changes are activated immediately upon entering the 'set' command.

Answer

The 'commit check' command activates the candidate configuration if syntax is valid.

Answer

The 'commit confirmed' command automatically commits changes permanently.

Question 7

During a routing table lookup, a packet matches both a static route and an OSPF route to the same destination. Which route will be installed in the forwarding table?

Accepted Answer

The static route, because it has a lower preference value.. In Junos, the route with the lowest preference value is installed in the forwarding table. Static routes have a default preference of 5, while OSPF internal routes have a default preference of 10. Therefore, the static route is preferred and installed.

Answer

Both routes, if they are equal-cost.

Answer

The route with the higher preference value.

Answer

The OSPF route, because OSPF is a dynamic routing protocol.

Question 8

A network administrator wants to filter routes from being installed in the routing table based on certain criteria. Which Junos feature should be used?

Accepted Answer

Routing policy (import). B is correct because a routing policy with an import term is the Junos mechanism to control which routes are accepted into the routing table from a routing protocol or a peer. By defining match conditions (e.g., prefix, community, AS path) and an action (accept or reject), the administrator can filter routes before they are installed. This is the standard Junos approach for route filtering at the routing table level.

Answer

Community list

Answer

Prefix list

Answer

Firewall filter

Question 9

A network engineer is configuring a new Juniper device and needs to ensure that the configuration is saved persistently across reboots. Which command should be used?

Accepted Answer

commit. The `commit` command activates the candidate configuration and saves it to the active configuration database, ensuring it persists across reboots. Without a commit, any changes made in candidate mode are lost when the device restarts.

Answer

save

Answer

request system reboot

Answer

show configuration

Question 10

Which TWO statements correctly describe the function of the 'commit' command in Junos OS? (Choose two.)

Accepted Answer

It validates the candidate configuration for syntax errors.. Option A is correct because the 'commit' command in Junos OS first validates the candidate configuration for syntax errors before applying it. If syntax errors are found, the commit fails and the candidate configuration is not applied, ensuring the device does not enter an inconsistent state. This validation step is a core part of Junos's transactional configuration model, where changes are staged in a candidate configuration and then committed atomically.

Answer

It schedules the configuration to be applied at a later time.

Answer

It discards the candidate configuration after saving.

Answer

It automatically reboots the device to apply the changes.

Question 11

An administrator needs to quickly revert all uncommitted configuration changes and return the device to the last committed configuration. Which command accomplishes this?

Accepted Answer

rollback 0. The command 'rollback 0' reverts all uncommitted configuration changes and returns the device to the last committed configuration. In Junos, the rollback command uses a numeric argument to specify which previous configuration to load, with 0 always referring to the most recently committed configuration. This effectively discards any pending changes in the candidate configuration without requiring a commit.

Answer

delete configuration

Answer

load override

Answer

rollback 1

Question 12

Based on the exhibit, what is the most likely reason for the ping failure?

Accepted Answer

The neighbor device is not configured or is unreachable.. The ping failure is most likely due to the neighbor device not being configured or unreachable because the output shows the interface is up (Physical link is Up) and the unit is enabled (Unit 0 is enabled), but there is no neighbor discovery or ARP entry. Without a valid next-hop or neighbor reachability, ICMP echo requests cannot be forwarded, resulting in ping failure.

Answer

A firewall filter is blocking ICMP traffic.

Answer

The interface is disabled at the unit level.

Answer

The interface is administratively down.

Question 13

A Juniper device is experiencing high CPU utilization due to a routing protocol process. The engineer suspects a specific BGP peer is causing the issue. Which operational command can be used to collect diagnostic information about the routing protocol processes?

Accepted Answer

show system processes extensive. Option A is correct because 'show system processes extensive' displays detailed CPU and memory usage for each individual process, including routing protocol daemons like bgpd. This allows the engineer to identify which specific BGP peer or process is consuming excessive CPU resources, rather than just seeing aggregate routing protocol statistics.

Answer

request support information

Answer

show bgp summary

Answer

monitor traffic interface

Question 14

Based on the exhibit, what is the most likely impact on the router?

Accepted Answer

Routing protocol adjacencies will be lost, causing routing instability.. The exhibit shows kernel messages indicating a hardware or software fault (e.g., a FPC crash or PIC restart). In Junos, such critical events cause the Packet Forwarding Engine (PFE) to reset, which tears down all routing protocol adjacencies (OSPF, BGP, IS-IS) because the control plane loses communication with the forwarding plane. This leads to route withdrawal and routing instability until the adjacencies are re-established.

Answer

The CPU will be overloaded due to the kernel messages.

Answer

The router will stop forwarding packets immediately.

Answer

The router will reboot automatically.

Question 15

A junior engineer is troubleshooting connectivity issues and wants to trace the path packets take to a remote destination. Which Junos command should be used?

Accepted Answer

traceroute. Option C is correct because the 'traceroute' command in Junos is specifically designed to trace the path packets take to a remote destination by sending UDP probes with increasing TTL values and analyzing ICMP Time Exceeded messages from intermediate routers. This directly addresses the junior engineer's need to map the Layer 3 path and identify where connectivity failures occur.

Answer

monitor traffic

Answer

show route

Answer

ping

Question 16

You are a network engineer at a service provider. You have a Juniper MX router that serves as a BGP route reflector for a large number of customer routes. Recently, the router has been experiencing high CPU utilization, and the BGP process (rpd) is consuming excessive memory. You suspect that the router is receiving too many routes from a specific BGP peer, causing the routing table to grow beyond the available memory. You need to diagnose the issue without affecting production traffic. Which course of action should you take?

Accepted Answer

Use the 'show route summary' command to check the routing table size and memory usage.. Option C is correct because the 'show route summary' command provides a high-level overview of the routing table size, including the total number of routes and the memory utilization of the routing table. This allows the engineer to quickly assess whether the routing table has grown beyond available memory without disrupting production traffic, which is the primary goal of the diagnosis.

Answer

Immediately shut down all BGP peers to stop the influx of routes.

Answer

Configure a prefix limit on all BGP peers.

Answer

Use the 'show bgp summary' command to check the number of prefixes per peer.

Question 17

Which TWO commands can be used to view the current operational state of an interface? (Choose two.)

Accepted Answer

show interfaces extensive. The 'show interfaces extensive' command displays detailed operational state information, including current status, errors, and statistics. The 'show interfaces terse' command provides a concise operational view showing interface names, administrative status, link status, and protocol families. Both commands query the current operational state of interfaces from the Junos OS kernel.

Answer

show log

Answer

show configuration interfaces

Answer

show route

Question 18

Refer to the exhibit. Based on the output, what is the operational status of interface ge-0/0/0?

Accepted Answer

The interface is administratively up and the link is up.. Option D is correct because the output shows 'Physical link is Up' and 'Administratively Up', confirming that the interface is both enabled and receiving a carrier signal. In JUNOS, the 'show interfaces terse' command displays 'up' for the administrative status and 'up' for the link status when both conditions are met.

Answer

The interface is up but the link is down.

Answer

The interface has no IP address configured.

Answer

The interface is administratively down.

Question 19

An engineer needs to apply a configuration change to the device, but only if the configuration is syntactically correct. Which command should be used before committing?

Accepted Answer

commit check. The 'commit check' command validates the candidate configuration for syntax errors without applying it, making it the correct choice when the engineer only wants to verify syntactic correctness before committing. Unlike 'commit', which applies changes immediately, 'commit check' performs the same validation as a commit but stops short of activating the configuration.

Answer

commit

Answer

commit confirmed

Answer

show | compare

Question 20

An administrator wants to navigate to the configuration mode to make changes to the device. Which command should be used?

Accepted Answer

configure. The correct command to enter configuration mode on a Juniper device is 'configure'. This command transitions the CLI from operational mode to configuration mode, allowing the administrator to make changes to the device's configuration. In JUNOS, the CLI has two distinct modes: operational mode (for monitoring and troubleshooting) and configuration mode (for modifying the active or candidate configuration).

Answer

set

Answer

edit

Answer

cli

JNCIA-JUNOS Practice Test 3 — 25 Questions

Exhibit

JNCIA-JUNOS Practice Test 3 — 25 Questions

Exhibit