JN0104 Junos, Associate (JNCIAJunos) Free Practice Test — 30 Questions

Question 1

Following a configuration commit on a Juniper Networks device that modifies the OSPF `reference-bandwidth` from its default value, which operational command output would most directly indicate the protocol\'s adaptation to the altered metric calculation and potential route recalculation?

Accepted Answer

show ospf database and show route protocol ospf

Question 2

Anya, a network engineer, is troubleshooting an intermittent connectivity issue on a Juniper SRX Series firewall. An internal subnet, previously accessible from external networks, is now sporadically unreachable. She has confirmed that the SRX is running OSPF to exchange routing information with adjacent routers. During her investigation, she notices that the SRX\'s packet forwarding behavior appears unusual when attempting to reach the affected subnet, suggesting a routing problem rather than a simple interface failure. She suspects a recent configuration change related to either OSPF or the firewall\'s security policies might be the culprit.

Which of the following Junos OS configuration aspects is most likely to cause intermittent reachability issues for internal subnets due to OSPF misconfiguration on an SRX, particularly when security policies are involved?

Accepted Answer

Security policies incorrectly filtering or mishandling OSPF control plane traffic or its interaction with the forwarding plane.

Question 3

A senior network engineer is meticulously configuring advanced routing policies on a Juniper MX Series router running Junos OS. They have made several modifications within the configuration mode, including route filtering and policy statements, but have not yet executed a commit operation. Before proceeding to a critical client meeting, the engineer realizes they need to discard all these unsaved changes and return the device to its last known stable configuration without affecting any previously committed operational parameters. Which of the following commands, when executed from configuration mode, will achieve this specific objective?

Accepted Answer

rollback 0

Question 4

A network administrator is configuring a new routing policy on a Juniper MX Series router running Junos OS. The policy involves complex prefix-list matching and route-to-next-hop actions. During the commit process, the administrator receives an error indicating a logical inconsistency between a defined prefix and an associated next-hop address that is not reachable within the current routing table. Which Junos OS behavior will ensure the router\'s operational integrity following this failed commit attempt?

Accepted Answer

The Junos OS will automatically roll back the entire configuration to the last successfully committed state.

Question 5

Anya, a network administrator managing a critical Junos-based network segment, is investigating persistent performance degradation. Users report intermittent connectivity issues, characterized by noticeable delays and occasional packet loss, primarily during periods of high network utilization. Anya suspects that an improperly configured Quality of Service (QoS) policy might be the root cause. She needs to identify which specific Junos CoS configuration element is most likely to directly induce such symptoms when misapplied, leading to unfair bandwidth allocation or congestion during traffic bursts.

Accepted Answer

Traffic control profiles that define shaping and policing rates

Question 6

Consider a Junos OS routing policy configuration. A policy named `RTR-POLICY` has two terms: `TERM1` which accepts BGP routes originating from AS 65000 and tagged with community `65000:100`, and `TERM2` which rejects OSPF routes matching the exact prefix `192.168.1.0/24`. If a BGP route for prefix `10.10.10.0/24` with community `65000:100` is advertised, what will be the ultimate disposition of this route according to `RTR-POLICY`?

Accepted Answer

Accepted due to matching the BGP protocol and community in TERM1.

Question 7

Anya, a network engineer tasked with enhancing the user experience on a corporate network, needs to implement a differentiated service for Voice over IP (VoIP) traffic traversing a Juniper SRX Series firewall. The objective is to ensure that VoIP packets receive preferential treatment, minimizing jitter and latency, while standard web browsing traffic is treated with a lower priority. The existing SRX configuration is extensive and lacks detailed documentation, presenting a challenge in identifying the most suitable Junos OS feature for this task without causing unintended network disruptions. Which Junos OS functionality is most appropriate for Anya to leverage for this specific traffic prioritization requirement?

Accepted Answer

Configuring Quality of Service (QoS) using firewall filters for traffic classification and mapping to forwarding classes with appropriate scheduling.

Question 8

Consider a network administrator managing a Juniper MX Series router running Junos OS. After committing a series of network policy adjustments, the administrator realizes a critical oversight in a specific access control list (ACL) rule that was part of the recent commit. The administrator then initiates a rollback operation targeting only the specific ACL rule that was incorrectly configured, aiming to revert it to its prior state without affecting other unrelated configuration parameters that were also part of the same commit. If other configuration parameters were modified *after* the initial commit, but *before* the rollback command was issued, and these modifications were not explicitly included in the rollback target, what will be the state of these other configuration parameters after the rollback operation completes?

Accepted Answer

They will retain their most recently modified state, as the rollback operation was targeted and did not encompass these independent changes.

Question 9

A network engineer is tasked with updating the hostname and several routing policies on a Juniper MX Series router running Junos OS. They first execute `load override /var/tmp/new_config.conf`, which contains a complete system configuration including a new hostname. Immediately following this, they issue the command `set policy-options policy-statement BGP-IN term 10 then accept`. At this juncture, before any commit operation has been performed, what is the state of the configuration on the router regarding these specific changes?

Accepted Answer

The new hostname and the modified routing policy exist only within the candidate configuration and have not yet affected the operational state of the router.

Question 10

Following a network maintenance event, Engineer Anya, while connected to a Juniper device via SSH, applies a critical routing policy change using the command `commit confirmed`. She then realizes an additional, minor modification to an interface description is also necessary and proceeds to apply this second change with a standard `commit` command. If Anya does not interact with the device further, what will be the state of the Junos configuration after the default 10-minute confirmation timer for the initial routing policy change expires?

Accepted Answer

The configuration will reflect the changes from the second, standard commit.

Question 11

Anya, a network engineer managing a critical Juniper SRX Series device, observes intermittent flapping of a BGP session with a key business partner. This instability began precisely after she committed a configuration change that adjusted the `local-preference` value for a specific route advertisement originating from her network. She needs to determine the fundamental Junos behavior that would explain this immediate impact on the BGP session without an explicit protocol restart. Which of the following Junos operational principles best accounts for the observed BGP session flapping following the `local-preference` modification?

Accepted Answer

Junos dynamically applies configuration changes affecting BGP, leading to immediate re-evaluation of routes and potential session re-establishment based on the updated path attributes.

Question 12

Consider a scenario where a router running Junos OS receives a BGP update for the route 192.168.1.0/24. This update is subject to a routing policy named "INBOUND-POLICY" which contains the following terms:

Term 1:
  From:
    Prefix-list: [ 192.168.0.0/16, 10.0.0.0/8 ]
  Then:
    Accept

Term 2:
  From:
    Prefix-list: [ 172.16.0.0/12 ]
  Then:
    Reject

Term 3:
  From:
    Prefix-list: [ 192.168.1.0/24 ]
  Then:
    Accept

What will be the final disposition of the route 192.168.1.0/24 as it is processed by "INBOUND-POLICY"?

Accepted Answer

The route is accepted by Term 1.

Question 13

Anya, a network administrator managing a Junos OS-based infrastructure, is troubleshooting an application that is experiencing significant packet loss and latency. Initial diagnostics suggest that the traffic for this specific application is not being routed along the most optimal paths, especially during periods of high network utilization. Anya needs to implement a Junos OS solution that allows her to define forwarding behavior based on specific traffic characteristics, such as source IP, destination port, and DSCP markings, to ensure this critical application\'s data takes a preferred route. Which Junos OS feature directly addresses this requirement for granular, policy-driven traffic forwarding?

Accepted Answer

Policy-Based Routing (PBR)

Question 14

A senior network engineer, after successfully authenticating with their credentials on a Juniper SRX firewall running Junos OS, finds themselves unable to enter configuration mode using the `configure` command. They can execute operational commands like `show version` and `show interfaces terse`. Upon investigation, it\'s determined that the engineer is assigned to a pre-defined login class that has been carefully curated for operational oversight rather than direct configuration changes. What specific permission, most likely absent from the engineer\'s assigned login class, is preventing them from entering configuration mode?

Accepted Answer

configure

Question 15

Anya, a network engineer deploying a new Juniper MX Series router for a remote branch office, is configuring routing policies. Her objective is to ensure that routes learned via BGP are always preferred over OSPF-learned routes for a specific network prefix, even if the OSPF routes appear to have more favorable administrative attributes. After configuring a higher `local-preference` on the BGP routes and a lower `metric` on the OSPF routes, she observes that the OSPF routes are still being selected by the router. Which core Junos OS routing selection mechanism, operating at a fundamental level, is most likely causing this outcome, overriding the locally configured attributes?

Accepted Answer

The inherent protocol preference values assigned by Junos OS to different routing protocols.

Question 16

Anya, a network engineer at a large financial institution, is grappling with a persistent, intermittent connectivity degradation impacting a crucial client trading platform. Users report sporadic packet loss and noticeable increases in latency, leading to transaction failures. Anya has already meticulously examined the physical layer, verifying cable integrity, transceiver health, and interface error counters, finding no anomalies. She then progressed to the data link layer, confirming proper VLAN tagging, checking for STP loops, and ensuring MAC address table stability, again with no clear culprit. Now facing continued ambiguity at the network layer, she is considering her next diagnostic action. Which of the following actions would represent the most effective and comprehensive next step in diagnosing this elusive issue?

Accepted Answer

Utilize Juniper's integrated traffic monitoring and performance analysis tools to capture and analyze real-time packet flow and system resource utilization across multiple layers.

Question 17

Anya, a network engineer managing a Juniper SRX firewall, observes that specific internal network prefixes are no longer being advertised to a particular BGP peer after a routine configuration update. The BGP session with this peer remains established, and the prefixes are present and active in the SRX’s routing table. Anya has reviewed the BGP configuration for the peer and confirms no explicit `reject` or `deny` statements are applied within the peer’s policy configuration that would target these prefixes. However, the prefixes are consistently absent from the peer’s received routes. What is the most probable underlying cause for this selective route advertisement failure?

Accepted Answer

An implicit rejection of the routes by the applied BGP routing policy due to a lack of an explicit `accept` or `next-policy` statement that matches these specific prefixes.

Question 18

A network administrator is tasked with rapidly assessing the health of a Juniper SRX firewall after a recent software update. The administrator needs to quickly verify that all configured network interfaces are administratively enabled and are currently passing traffic, and to see if any logical configurations such as assigned IP addresses are active. Which operational mode command in Junos would provide the most concise and relevant overview of this interface status across the entire device?

Accepted Answer

show interfaces terse

Question 19

Anya, a network engineer, is troubleshooting BGP routing on a Juniper MX Series router. She observes that a specific network prefix is reachable via two different paths. Path A has a local preference of 150, and Path B has a local preference of 200. According to standard BGP path selection, Path A should be preferred due to its lower local preference value. However, the router is consistently selecting Path B. Anya has verified that no other BGP attributes (AS_PATH length, origin type, MED) are influencing the selection in a way that would override the local preference. What specific Junos-implemented BGP attribute, evaluated prior to local preference, is most likely configured to cause this deviation from the expected local preference-based selection?

Accepted Answer

Weight

Question 20

A network administrator is configuring a virtual routing instance on a Juniper device running Junos OS. The requirement is to ensure that any traffic destined for an IP address for which no explicit route exists within this specific routing instance is immediately discarded, rather than being subject to a default tunnel encapsulation. Which Junos OS configuration statement, when applied to the routing instance, achieves this precise behavior?

Accepted Answer

`set routing-instances no-tunnel-all`

Question 21

A network engineer is tasked with implementing a new BGP peering session with a partner organization. After meticulously crafting the configuration statements in Junos OS, including neighbor definitions, authentication, and routing policy application, the engineer enters configuration mode and applies the changes. The modifications are now present in the system but are not yet active. What is the specific Junos OS operational command that will activate these pending configuration changes, making them the new running configuration?

Accepted Answer

commit

Question 22

During a routine network maintenance operation on a Juniper MX series router running Junos OS, a network engineer attempts to implement a complex set of routing policy modifications. Upon executing the `commit` command, the operation fails due to an unforeseen dependency conflict between the new policy statements and existing interface configurations. Considering the operational state of the router immediately after this failed commit, which of the following best describes the system\'s configuration status?

Accepted Answer

The active configuration remains unchanged, and the candidate configuration contains the uncommitted, erroneous changes.

Question 23

Anya, a network engineer managing a large enterprise network, is troubleshooting a Juniper MX Series router experiencing intermittent packet loss and increased latency affecting voice and video communications. Upon reviewing the router\'s configuration, she notices that both FTP and SSH services are enabled within the `[edit system services]` hierarchy. Considering the impact of management plane services on data plane performance, which of the following adjustments to the router\'s configuration would most effectively mitigate potential resource contention and improve the forwarding of real-time traffic?

Accepted Answer

Disable the FTP service.

Question 24

Anya, a network administrator for a rapidly expanding enterprise, is tasked with enforcing a new security directive that mandates highly specific access controls for internal server management interfaces. The existing network infrastructure, built on Juniper devices running Junos OS, currently permits broader access than is acceptable under the new policy. Anya needs to implement a solution that ensures only authenticated and authorized personnel can manage these critical servers, restricting access based on both user identity and the originating network segment. Which Junos OS feature set is most directly applicable to achieving this granular, identity-aware control over device management access?

Accepted Answer

Configuring AAA services in conjunction with granular user roles and permissions.

Question 25

Anya, a network administrator for a growing e-commerce platform, is tasked with rapidly implementing a new security policy on their Juniper SRX Series firewall. A critical zero-day vulnerability has been identified, requiring the immediate blocking of traffic associated with a specific exploit signature. Anya has a narrow window of opportunity to deploy this measure before peak sales hours commence, and the solution must allow for future signature updates without extensive manual reconfiguration. Which Junos OS security feature is most directly suited for dynamically identifying and blocking traffic based on such evolving threat signatures, ensuring timely protection and adaptability?

Accepted Answer

Intrusion Prevention System (IPS)

Question 26

When a routing policy is applied to an interface in Junos OS, and a received routing update satisfies all the match conditions within a specific policy term, what is the immediate and primary consequence regarding the policy\'s subsequent evaluation for that particular routing update?

Accepted Answer

Junos ceases to evaluate any further terms within that applied routing policy for the matched routing update.

Question 27

Consider a Juniper Networks device running Junos OS. The current operational configuration includes the statement `set system ntp server 192.0.2.1`. An administrator then commits a new configuration snippet that contains only the statement `set system ntp server 192.0.2.2`. Following this commit operation, what will be the effective NTP server configuration on the device?

Accepted Answer

The device will be configured to use only 192.0.2.2 as its NTP server.

Question 28

Anya, a network engineer responsible for a critical client\'s network, is alerted to a complete service interruption affecting their primary data center connectivity. The network relies on a Juniper SRX Series device acting as the edge firewall. With the client experiencing significant business impact, Anya must rapidly identify the cause and restore service. She immediately begins a systematic diagnostic process, prioritizing swift resolution while ensuring accurate root cause identification. Which combination of behavioral competencies and technical actions best characterizes Anya\'s effective response to this high-pressure situation?

Accepted Answer

Demonstrating adaptability by quickly pivoting troubleshooting steps, utilizing Junos operational commands such as `show system commit`, `show log messages`, and `show security flow session` to isolate the failure point and communicate status updates to the client.

Question 29

A network engineer is tasked with optimizing traffic flow on a Juniper MX Series router to guarantee a consistent quality of service for an enterprise Voice over IP (VoIP) application, while simultaneously preventing large, non-time-sensitive file transfers from monopolizing available bandwidth. The engineer needs to implement a configuration that limits the maximum throughput for the file transfer traffic to 50 Mbps, ensuring it does not negatively impact the VoIP service, which is classified into a higher priority queue. Which Junos OS configuration element is primarily responsible for enforcing such a strict upper bandwidth limit on a specific traffic flow, often in conjunction with classification and scheduling?

Accepted Answer

traffic-control-profile

Question 30

Anya, a network administrator, is troubleshooting an issue where management traffic originating from a Juniper SRX firewall is being routed out of an unintended egress interface. She has confirmed that the SRX has established proper OSPF adjacencies and that static routes are configured correctly for transit traffic. However, when attempting to access the SRX via SSH from an external network, the traffic is taking an unexpected path, suggesting a problem with how the firewall itself is making routing decisions for its own sourced packets. Upon reviewing the active configuration, Anya finds a policy statement applied to the routing instance that includes a term with the `next-hop self` action. What is the most direct consequence of this `next-hop self` action in the context of firewall-sourced traffic when a matching prefix is encountered in the policy?

Accepted Answer

The firewall will utilize its own interface as the next hop for the matching traffic, potentially overriding standard routing table lookups for locally originated packets.

JN0104 Junos, Associate (JNCIAJunos) Free Practice Test — 30 Questions

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