JN0649 Enterprise Routing and Switching, Professional (JNCIPENT) Free Practice Test — 30 Questions

Question 1

Anya, a senior network engineer, is troubleshooting a recently established BGP peering session with a critical business partner. The peering is exhibiting instability, with a significant number of routes from the partner network flapping due to policy violations. Upon investigation, Anya identifies that the partner is inadvertently advertising a substantial quantity of prefixes that are either unroutable within their own network or exceed the agreed-upon prefix length limitations stipulated in their interconnection agreement. Anya needs to implement a robust solution to filter these specific, problematic prefixes at the BGP session ingress without impacting the valid routes being exchanged. Which of the following strategies would be the most effective and efficient for Anya to implement on her Juniper Networks router?

Accepted Answer

Configure a prefix-list to deny the specific invalid and oversized prefixes, and apply this prefix-list within a BGP import route-map applied to the partner's peering session.

Question 2

Anya, a network engineer responsible for a critical enterprise network segment utilizing Juniper MX Series routers, is tasked with implementing a robust Quality of Service (QoS) policy. The objective is to guarantee low latency for VoIP communications, which utilize UDP ports 5060 for signaling and a dynamic range of UDP ports from 16384 to 32767 for Real-time Transport Protocol (RTP) streams. Simultaneously, she must ensure that bulk data transfers, specifically those using TCP port 21 for FTP, are managed to prevent network congestion while still allowing for reasonable throughput. Anya has already crafted a firewall filter that accurately classifies and assigns the VoIP signaling, RTP, and FTP traffic to distinct forwarding classes. However, the network still experiences occasional voice jitter during periods of high traffic volume. Which of the following configurations, when applied in conjunction with her existing filter, is most critical for ensuring that the classified VoIP traffic receives preferential treatment and meets its latency requirements, while also managing the bandwidth allocation for FTP traffic during congestion?

Accepted Answer

A scheduler map that associates the VoIP forwarding class with a strict-priority scheduling mechanism and the FTP forwarding class with a weighted-fair-queuing mechanism.

Question 3

Anya, a network engineer at a global enterprise, is investigating intermittent connectivity problems impacting a crucial customer-facing e-commerce platform. The network utilizes BGP extensively for inter-AS routing. She observes that traffic destined for a particular external network prefix is consistently routed through Autonomous System (AS) 65002, even though AS 65001 advertises the same prefix with a lower Multi-Exit Discriminator (MED) value. The internal routing policy within Anya\'s AS is designed to prefer paths with higher local preference. When analyzing the BGP routing table, she confirms that the path through AS 65002 has a higher local preference configured, while the path through AS 65001 has the lower MED but an equal or lower local preference. What is the most probable primary reason for the observed traffic routing behavior?

Accepted Answer

The router prioritizes the higher local preference attribute over the lower MED attribute when making its BGP path selection decision.

Question 4

A regional sales office reports that their Voice over IP (VoIP) calls are frequently breaking up, and video conference participants are experiencing significant lag and dropped frames. Network engineers have confirmed that the issue is not with the end-user devices themselves. The enterprise network utilizes a mix of Juniper and Cisco hardware, with multiple WAN links connecting to different data centers and cloud services. What is the most effective initial diagnostic methodology to identify the source of these intermittent performance degradations?

Accepted Answer

Execute targeted ICMP echo requests and traceroute commands from affected client workstations to a representative internal server and an external internet destination, meticulously analyzing packet loss percentages and round-trip times at each hop.

Question 5

A large enterprise network, crucial for real-time financial transactions, is experiencing sporadic but disruptive connectivity degradations. Users report intermittent unreachability to critical application servers, accompanied by significant packet loss and fluctuating latency, particularly during peak operational hours. Network monitoring indicates no physical link failures or hardware malfunctions. The issue appears to stem from the routing infrastructure\'s inability to adapt efficiently to the dynamic nature of the traffic patterns and minor, transient link state changes. Which strategic adjustment to the network\'s Interior Gateway Protocol (IGP) configuration would best address this scenario, focusing on enhancing adaptability and minimizing service disruption without introducing undue complexity or instability?

Accepted Answer

Implement a dynamic routing protocol feature that prioritizes rapid convergence through optimized flooding and faster link-state update processing, enabling quicker recalculation of optimal paths during transient network events.

Question 6

A network administrator is investigating a recurring issue where users in the Marketing department consistently report dropped VoIP calls and intermittent access to internal collaboration tools, while other departments remain unaffected. Initial diagnostics confirm that physical cabling and basic IP addressing are sound. Traceroute commands to external resources from affected workstations show timeouts after the third hop, but internal pings to other devices within the Marketing subnet are successful. The problem is most pronounced during peak usage hours. Based on common enterprise network design principles and potential Juniper device configurations, what is the most likely underlying cause for this specific set of symptoms?

Accepted Answer

An aggressive traffic policing policy is configured on an edge router or access switch, specifically targeting UDP traffic originating from or destined to the Marketing department's subnet, leading to packet drops during periods of high utilization.

Question 7

Anya, a network engineer for a large enterprise, is troubleshooting intermittent latency and packet loss issues affecting a critical customer onboarding service. She has identified that traffic to the customer\'s network is arriving via multiple upstream providers, and the current BGP path selection appears to be favoring paths that, while available, exhibit higher latency during peak hours. To improve the stability and performance of this service, Anya needs to influence the inbound path selection into her enterprise network. She wants to make the paths associated with higher latency links less attractive to external networks. Which BGP path manipulation technique would be most effective for Anya to implement to signal to external ASes that certain ingress points into her network should be avoided in favor of others, thereby steering traffic towards lower-latency paths?

Accepted Answer

AS-path prepending

Question 8

Anya, a seasoned network engineer managing a complex Juniper-based enterprise network, is troubleshooting intermittent packet loss and increased latency on a critical inter-data center link. Performance degradation is most noticeable during peak hours. Upon investigation of a core MX960 router on the path, she observes that the expedited-forwarding (EF) queue is consistently showing high buffer occupancy and experiencing drops, while the best-effort (BE) queue also exhibits significant utilization. Analysis of the class-of-service (CoS) configuration reveals that the EF queue has a limited buffer allocation, and while it has a guaranteed bandwidth, the ingress traffic bursts occasionally exceed the combined buffer capacity and guaranteed rate. The BE queue is configured with a larger buffer but lacks aggressive shaping. Which of the following actions would be the most appropriate initial step to alleviate the observed performance issues without immediately impacting other traffic classes or requiring a complete overhaul of the QoS policy?

Accepted Answer

Increase the buffer allocation for the expedited-forwarding queue and review its guaranteed bandwidth settings to better accommodate traffic bursts.

Question 9

A network administrator is tasked with resolving a complete communication failure between hosts residing in VLAN 10 (subnet 192.168.10.0/24) and VLAN 20 (subnet 192.168.20.0/24) within an enterprise network. The Layer 3 switch designated to handle inter-VLAN routing has configured Switched Virtual Interfaces (SVIs) for both VLANs, with the SVI for VLAN 10 set to 192.168.10.1/24 and the SVI for VLAN 20 set to 192.168.20.1/24. Host configurations, including IP addresses, subnet masks, and default gateways, have been verified and appear to be correct. The administrator has also confirmed that no access control lists are actively blocking traffic between these subnets and that the routing process is generally active on the switch. Considering these observations, what is the most probable underlying configuration oversight preventing successful inter-VLAN communication?

Accepted Answer

The global IP routing feature has not been enabled on the Layer 3 switch.

Question 10

A network administrator is tasked with troubleshooting why specific internal network prefixes are not being advertised via BGP to an external partner AS. The BGP session between the two edge routers is fully established, and the administrator has verified that the local router is receiving route updates from the external peer. Upon reviewing the outbound policy applied to the BGP neighbor, the administrator finds a route-map configured with a prefix-list that explicitly permits a defined set of internal IP address ranges. The route-map\'s final entry is a deny statement for any prefixes not matching the preceding permit statements. What is the most probable cause for the selective advertisement of BGP routes in this scenario?

Accepted Answer

The outbound route-map is effectively filtering advertisements, permitting only the prefixes explicitly defined in the associated prefix-list.

Question 11

Anya, a network engineer at a large financial institution, is implementing a new Quality of Service (QoS) policy on a Juniper MX Series router to manage traffic for a global video conferencing system and a critical VoIP telephony service. The primary objective is to guarantee a superior experience for voice calls, ensuring minimal delay and jitter, even during periods of peak network utilization. Given the sensitive nature of real-time voice communication, which queuing strategy would most effectively address the requirement for low latency and jitter for voice traffic when the link experiences congestion?

Accepted Answer

Strict Priority Queuing

Question 12

Anya, a network engineer responsible for a multi-site enterprise network, observes a significant degradation in application performance between two branch offices, specifically manifesting as increased latency and intermittent packet loss on their primary MPLS WAN link. The network utilizes Juniper MX Series routers at the edge and core, with MPLS and BGP VPN configured for inter-site connectivity. Anya needs to perform an initial diagnostic step to effectively pinpoint the root cause of this performance issue within the MPLS fabric. Which of the following actions represents the most direct and informative initial troubleshooting step for this scenario, focusing on the MPLS forwarding plane and control plane stability?

Accepted Answer

Verify the status of Label Distribution Protocol (LDP) adjacencies between the relevant edge and core routers and examine the health and operational state of the established Label Switched Paths (LSPs) for the affected traffic.

Question 13

A network administrator is configuring BGP on a Juniper router and observes three distinct paths to a particular /24 destination prefix. Path A is learned from a trusted internal peer with a locally configured Weight of 300. Path B is learned from an external peer with a Weight of 100 and a Local Preference of 150. Path C is learned from another internal peer with a Weight of 200, an AS_PATH length of 2, and a Local Preference of 120. Assuming all other BGP attributes are identical or not relevant for the selection among these three paths, which path will the router select as the best path?

Accepted Answer

Path A

Question 14

A network engineer is configuring a complex enterprise network where multiple routing protocols are simultaneously active to provide redundancy and optimal path selection. A specific destination network, 192.168.10.0/24, is reachable through three distinct routing protocols: OSPF, EIGRP, and BGP. The router has received a route for this destination via OSPF with a default administrative distance, an EIGRP route with its default administrative distance, and a BGP route with its default administrative distance. Additionally, an OSPF Area Border Router (ABR) is advertising a Type 5 LSA summary route covering the 192.168.8.0/21 range, which encompasses the 192.168.10.0/24 network. Considering the default administrative distances for these protocols and the behavior of route summarization within OSPF, which route will the edge router install in its IP routing table for the destination 192.168.10.0/24, and why?

Accepted Answer

The BGP route, because BGP has the lowest administrative distance (20) compared to EIGRP (90) and OSPF (110), and administrative distance is evaluated before the longest prefix match when routes are learned from different protocols.

Question 15

Anya, a senior network engineer managing a large, multi-vendor enterprise network, is tasked with implementing a critical routing policy update that will significantly alter traffic engineering paths. The network comprises Juniper, Cisco, and Huawei devices, each with its own proprietary extensions and default behaviors for routing protocols like BGP and OSPF. Anya anticipates that the implementation will require meticulous, device-by-device configuration changes, and she foresees challenges in adapting the policy quickly if unforeseen network events occur or if business priorities shift mid-deployment. Which of the following approaches would best equip Anya to manage the complexity, maintain effectiveness during transitions, and pivot strategies efficiently in this dynamic environment?

Accepted Answer

Employing a network orchestration platform that can interpret and translate the routing policy into vendor-specific configurations, enabling centralized management and dynamic policy adjustments across the heterogeneous infrastructure.

Question 16

A network administrator is troubleshooting an OSPF deployment within a large enterprise. While all expected OSPF LSAs are populating the Link State Database (LSDB) on routers in Area 1, routes to an external network segment, 10.10.50.0/24, which are advertised via Type 5 LSAs, are not appearing in the routing tables of routers within Area 1. The Type 5 LSAs for this network are indeed present in the LSDB. Considering the OSPF SPF algorithm\'s process for handling external routes, what is the most critical factor that could lead to this specific symptom, where the LSA exists but the route is absent from the routing table?

Accepted Answer

The forward address within the Type 5 LSA is set to 0.0.0.0, and the ASBR is unable to provide a valid next-hop to the external network.

Question 17

During a critical service outage impacting a financial trading platform, network engineers discover that a specific customer prefix is not reachable due to suboptimal BGP path selection on a Juniper MX Series router. Analysis of the `show route protocol bgp extensive` output for the affected prefix reveals that a particular learned route is being assigned a `local-preference` value significantly lower than expected, causing downstream routers to avoid this path. This incorrect attribute assignment is traced back to a routing policy applied to inbound BGP updates from a specific peer. Which of the following actions would most effectively restore optimal routing for the affected prefix without introducing new policy complexities or impacting other critical routes?

Accepted Answer

Modify the existing routing policy to remove the explicit `local-preference` setting for the affected prefix, allowing BGP to utilize its default or other path selection attributes.

Question 18

Anya, a network engineer, is troubleshooting intermittent connectivity and high latency issues affecting a specific subnet within her enterprise network. These problems began shortly after a planned upgrade that integrated a new OSPF domain with an existing IS-IS domain through route redistribution. Initial checks confirm stable Layer 1 and Layer 2 connectivity, and OSPF neighbor states and IS-IS adjacencies appear nominal, though some routers show brief adjacency flaps during periods of high traffic. Anya suspects the redistribution process might be contributing to the instability. Which of the following scenarios is most likely to manifest as intermittent packet loss and high latency in this context, stemming from the interaction between the two routing protocols?

Accepted Answer

Aggressive route summarization at the OSPF-IS-IS redistribution point, leading to incomplete routing information for specific prefixes and suboptimal path selection during convergence events.

Question 19

Anya, a senior network architect, is tasked with updating a large enterprise\'s core routing infrastructure to comply with a new, stringent data privacy regulation that mandates end-to-end encryption for all inter-site traffic within 90 days. The current network utilizes a mix of BGP and OSPF, with established QoS policies that are critical for voice and video services. The project was initially scoped for a six-month, phased implementation focusing on gradual upgrades. However, the new regulation\'s aggressive timeline forces Anya to reconsider the entire approach. She must now evaluate how to integrate robust encryption without compromising existing performance guarantees or introducing complex interoperability issues between diverse network segments. Her team is experienced but accustomed to a more deliberate pace. Which of the following strategic adjustments would best demonstrate Anya\'s adaptability and leadership in this high-pressure, ambiguous situation, leveraging her technical expertise for rapid, effective resolution?

Accepted Answer

Immediately implement a mandatory, network-wide IPsec tunnel overlay using pre-shared keys for all inter-site links, while simultaneously initiating a review of OSPF and BGP configurations for potential security attribute integration, and communicating a revised, accelerated project plan with clear interim milestones to the team.

Question 20

Anya, a network engineer, is implementing a Quality of Service (QoS) strategy on a Juniper MX Series router to ensure voice traffic, identified by DSCP EF markings, receives preferential treatment through a strict-priority queuing mechanism. She needs to configure the router to correctly classify, queue, and transmit these packets. Considering the typical Junos OS QoS configuration hierarchy, which of the following configuration elements, when considered in isolation, is LEAST directly responsible for ensuring that traffic marked with DSCP EF is placed into a strict-priority queue?

Accepted Answer

The definition of a forwarding class to represent voice traffic.

Question 21

Consider an OSPF network segment where Router B is directly connected to Router C, and Router C is directly connected to Router A. Router B originates a Link State Advertisement (LSA) for its connected segment. Router C receives this LSA, but upon validation, detects an invalid checksum within the LSA packet. What immediate action will Router C take regarding this LSA, and what will be the consequence for its communication with Router A concerning this specific LSA?

Accepted Answer

Router C will discard the LSA and send a Link State Acknowledgment (LSACK) to Router B, preventing the invalid LSA from being flooded to Router A.

Question 22

A network administrator notices that after deploying a new enterprise resource planning (ERP) system that heavily utilizes multicast for real-time data dissemination, users connected to VLAN 30 are reporting intermittent packet loss and elevated latency. Network monitoring tools indicate that the issue primarily occurs during peak usage hours of the ERP system, and the problem seems localized to traffic traversing the distribution layer switches. The existing network infrastructure is a hierarchical design with access layer switches aggregating user traffic and distribution layer switches providing inter-VLAN routing and aggregation. The administrator needs to ensure the reliability and performance of the new ERP system\'s multicast traffic without unduly impacting other network services. Which of the following actions would most effectively resolve the observed performance degradation for the ERP multicast traffic?

Accepted Answer

Configure strict priority queuing on the egress interfaces of the distribution layer switches for traffic classified as belonging to the ERP system's multicast streams within VLAN 30.

Question 23

A financial services firm reports intermittent packet loss and elevated latency affecting their critical trading applications. Initial investigations by the network operations team confirm that BGP peering is stable, and routing tables reflect expected path selections for the client\'s subnets. However, the performance issues persist, jeopardizing real-time transaction processing. Considering the client\'s stringent Service Level Agreement (SLA) which guarantees a maximum of 0.5% packet loss and sub-10ms latency, what is the most effective next step to diagnose and resolve this issue?

Accepted Answer

Analyze interface statistics for physical layer errors, discards, and utilization on all relevant network segments, including those connecting to the client and the upstream provider, and cross-reference these findings with the client's SLA parameters.

Question 24

A network administrator is troubleshooting an enterprise OSPF deployment where routers are experiencing frequent adjacency flaps. The current OSPF configuration on all participating routers sets the Hello Interval to 10 seconds and the Dead Interval to 30 seconds. During periods of minor network congestion, these adjacency flaps become more pronounced, leading to routing instability. The administrator wants to implement a change that will increase the resilience of OSPF adjacencies to temporary packet loss and network latency without unduly delaying the detection of actual failures.

Which adjustment to the OSPF timers would most effectively address the observed adjacency flapping issue while maintaining a reasonable convergence time?

Accepted Answer

Increase the OSPF Dead Interval to 60 seconds while keeping the Hello Interval at 10 seconds.

Question 25

Anya, a network administrator, is tasked with diagnosing why internal users on a corporate network can no longer access a critical external SaaS application hosted at IP address $203.0.113.10$, while external users can still access internal resources hosted at $192.168.1.50$. The Juniper SRX Series firewall is positioned at the network edge, with an internal zone named `LAN` and an external zone named `WAN`. Anya has confirmed that the firewall is passing traffic in the reverse direction (WAN to LAN) without issue, indicating that the stateful inspection engine is operational for established sessions. Given the observed behavior and the zone-based security architecture of the SRX, what is the most probable cause and immediate corrective action required to restore the internal users\' access to the SaaS application?

Accepted Answer

A security policy is missing or incorrectly configured to permit traffic originating from the `LAN` zone destined for the `WAN` zone, specifically allowing the protocol and port used by the SaaS application to reach $203.0.113.10$.

Question 26

Following a network infrastructure upgrade and subsequent maintenance window, a network operations team observes a significant increase in application latency and intermittent packet loss for a critical financial trading platform. Initial diagnostics confirm that BGP peering sessions remain stable, and no explicit policy changes were intended to alter routing behavior. However, traceroute outputs and BGP best path selection analysis reveal that traffic is now traversing a considerably longer and less performant path than before the maintenance. Which BGP path selection attribute is the most probable initial focus for investigation to address this sudden suboptimal path selection, assuming the goal is to restore traffic flow over the previously preferred, more efficient routes?

Accepted Answer

Local Preference

Question 27

A network administrator is investigating recurring, sporadic connectivity failures affecting a segment of users attempting to access a critical server farm. Initial diagnostics confirm that physical layer integrity and data link layer protocols are functioning correctly, and basic IP reachability between the affected client subnets and the server farm exists. However, a noticeable percentage of packets are being dropped, with the loss rate fluctuating throughout the day and not correlating with any specific time or event. The administrator suspects a configuration issue that dynamically impacts traffic flow rather than a static misconfiguration. Which of the following network service configurations is the most probable cause for this intermittent packet loss, demanding a strategic pivot in troubleshooting approach?

Accepted Answer

An ingress policing policy on an aggregation switch, configured with overly stringent rate limits for a specific traffic class originating from the affected client subnets.

Question 28

Anya, a network engineer at a growing enterprise, is troubleshooting a persistent problem where workstations in subnet 192.168.10.0/24 (VLAN 10) cannot reach servers in subnet 192.168.20.0/24 (VLAN 20). The Juniper SRX Series firewall is configured as the Layer 3 gateway for both VLANs, with separate IRB interfaces configured for each VLAN. IP addressing and subnet masks are verified as correct on all hosts and the SRX. The SRX\'s routing table correctly shows directly connected routes for both 192.168.10.0/24 and 192.168.20.0/24, and ARP entries on the SRX accurately map gateway MAC addresses. Despite these confirmations, inter-VLAN communication fails. What is the most likely underlying cause of this communication breakdown on the SRX?

Accepted Answer

A security policy is not configured to permit traffic flow between the security zones associated with VLAN 10 and VLAN 20.

Question 29

Anya, a network engineer responsible for a critical enterprise network, has recently established a new BGP peering session with a partner organization. The BGP session itself is stable and operational, with route information being exchanged. However, users are reporting intermittent and selective connectivity failures to specific services hosted within the partner network. Anya has confirmed that the BGP neighbor is up and that routes are present in the routing table, but the traffic does not traverse as expected. Considering the nuanced control mechanisms available in enterprise routing policies, which Junos OS configuration element is most likely the direct cause of these specific traffic flow disruptions, allowing the BGP session to remain active but selectively blocking certain routes or traffic patterns?

Accepted Answer

A route-map applied to the BGP neighbor that explicitly denies specific prefixes or attributes.

Question 30

Anya, a network engineer responsible for a critical enterprise WAN link, is tasked with ensuring that voice and video conferencing traffic consistently meets stringent Quality of Service (QoS) requirements, specifically targeting low latency and minimal jitter, even during periods of high network utilization. Existing network monitoring indicates that while traffic is classified and assigned to appropriate forwarding classes, intermittent packet loss and increased latency are observed for these sensitive real-time flows when bulk data transfer applications experience significant throughput. Anya needs to implement a configuration that actively controls the transmission rate of the prioritized traffic to prevent it from exceeding a defined bandwidth allocation and to smooth out bursts, thereby guaranteeing its performance characteristics. Which of the following actions, when applied to the identified real-time traffic, would most effectively achieve this performance guarantee?

Accepted Answer

Implementing egress traffic shaping on the prioritized flows to a specific committed information rate.

JN0649 Enterprise Routing and Switching, Professional (JNCIPENT) Free Practice Test — 30 Questions

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