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Question 321

Which Junos feature protects routing engines from unwanted traffic?

1. Control-plane protection
2. Port mirroring
3. Link aggregation
4. Route aggregation

Correct Answer: 1

Explanation:

Control-plane protection mechanisms help protect the Routing Engine from excessive or unwanted traffic directed toward processes responsible for routing and device control. Unlike ordinary transit traffic handled by the forwarding plane, control-plane traffic can consume resources needed for routing protocols and system management. Appropriate filtering and rate-control mechanisms can therefore help preserve control-plane stability during abnormal traffic conditions. Port mirroring provides traffic visibility, link aggregation combines physical interfaces, and route aggregation reduces routing information. Control-plane protection is consequently concerned specifically with safeguarding the device’s control functions.

Question 322

Which Junos architecture component handles centralized device control functions?

1. Packet Forwarding Engine
2. Routing Engine
3. Flexible PIC Concentrator
4. Interface Controller

Correct Answer: 2

Explanation:

The Routing Engine is responsible for major control-plane functions within Junos architecture. It runs routing protocols, maintains routing information, handles system management functions, and communicates with the forwarding plane. The Packet Forwarding Engine is responsible primarily for high-speed packet forwarding. Interface-related components provide physical or logical connectivity functions rather than serving as the central control processor. Understanding the separation between control-plane and forwarding-plane responsibilities is important for troubleshooting Junos platforms. A problem affecting the Routing Engine can influence routing and management even when packet forwarding may continue under certain circumstances.

Question 323

Which chassis capability maintains control during Routing Engine failure?

1. Graceful Routing Engine Switchover
2. Route aggregation
3. Link protection
4. Packet sampling

Correct Answer: 1

Explanation:

Graceful Routing Engine Switchover, or GRES, allows a Junos device with redundant Routing Engines to transition control between them while attempting to preserve forwarding continuity. The feature is designed to reduce disruption when the master Routing Engine becomes unavailable. Route aggregation concerns routing-table reduction, link protection concerns network-path resilience, and packet sampling provides traffic statistics. GRES is therefore specifically associated with redundancy between Routing Engines. Its behavior should be considered together with other high-availability mechanisms because maintaining forwarding and preserving protocol state can require additional capabilities.

Question 324

Which Junos feature preserves protocol state during Routing Engine switchover?

1. Storm control
2. NSR
3. LLDP
4. Port security

Correct Answer: 2

Explanation:

Nonstop Active Routing, or NSR, helps preserve routing protocol state during a Routing Engine switchover. By maintaining relevant protocol information across redundant control components, NSR can reduce the need for routing neighbors to rebuild sessions after a control-plane transition. This is different from ordinary redundancy, where a switchover might cause protocol sessions to restart. Storm control limits excessive Layer 2 traffic, LLDP discovers neighbors, and port security controls device access. NSR therefore focuses specifically on preserving routing protocol continuity during Routing Engine redundancy events.

Question 325

Which Junos upgrade method minimizes service interruption during software updates?

1. ISSU
2. ARP
3. ECMP
4. DHCP

Correct Answer: 1

Explanation:

In-Service Software Upgrade, or ISSU, is designed to reduce service disruption while upgrading software on supported Junos platforms. The exact behavior and supported upgrade scenarios depend on platform architecture and software release. The purpose is to allow software maintenance while minimizing interruption to network services. ARP performs IPv4 address resolution, ECMP distributes traffic among equal-cost paths, and DHCP provides dynamic host configuration. ISSU is therefore the feature specifically associated with maintaining network service during certain software upgrade procedures. Administrators should verify platform and release support before performing an ISSU operation.

Question 326

Which hardware component houses multiple interface cards within chassis?

1. FPC
2. PIC
3. Transceiver
4. Interface unit

Correct Answer: 1

Explanation:

A Flexible PIC Concentrator, or FPC, is a chassis component designed to contain one or more Packet Forwarding Engine-related interface modules depending on the Junos platform. PICs provide specific physical interface functionality and are associated with FPC slots on supported modular systems. A transceiver is a smaller physical component used with certain interfaces, while an interface unit represents a logical configuration concept rather than the chassis component described here. Understanding the relationship between FPCs and PICs helps administrators identify hardware locations and interpret chassis inventory information.

Question 327

Which hardware component provides physical interface connectivity?

1. FPC
2. PIC
3. Routing Engine
4. Power module

Correct Answer: 2

Explanation:

A Physical Interface Card, or PIC, provides physical interface connectivity on supported Juniper modular platforms. PICs contain interface ports or related physical connectivity hardware and are associated with specific FPC locations depending on the chassis design. The FPC provides the broader hardware container or forwarding component relationship, while the Routing Engine performs control-plane processing. A power module supplies electrical power rather than network connectivity. Recognizing the PIC’s role helps when identifying interface hardware, interpreting chassis inventory, and planning interface expansion on modular Junos systems.

Question 328

Which Junos feature creates independent administrative environments?

1. Logical systems
2. Route reflection
3. Prefix filtering
4. Link aggregation

Correct Answer: 1

Explanation:

Logical systems allow a supported Junos device to be divided into multiple independent logical environments. Each logical system can maintain separate configuration, interfaces, routing information, and administrative access according to the platform’s capabilities. This can be useful for service-provider environments, managed services, or situations where multiple administrative domains must share physical hardware. Route reflection concerns BGP scalability, prefix filtering controls route selection, and link aggregation combines physical links. Logical systems therefore provide a mechanism for creating distinct logical device environments on a shared physical Junos platform.

Question 329

Which CoS component assigns packets into forwarding classes?

1. Scheduler
2. Classifier
3. Policer
4. Rewrite rule

Correct Answer: 2

Explanation:

A CoS classifier examines packet characteristics and assigns traffic to an appropriate forwarding class. Classification provides the foundation for subsequent quality-of-service treatment because forwarding classes can determine queue selection, scheduling behavior, and other traffic-handling decisions. A scheduler determines how queued traffic receives transmission opportunities, a policer enforces traffic-rate limits, and a rewrite rule changes packet markings. The classifier therefore performs the initial categorization function within a CoS design. Correct classification is important because later traffic treatment depends on the forwarding class assigned to each packet.

Question 330

Which CoS attribute represents packet drop precedence?

1. Loss priority
2. Forwarding class
3. Scheduler map
4. Rewrite table

Correct Answer: 1

Explanation:

Loss priority identifies the relative likelihood that packets may be discarded during congestion. CoS configurations can use loss-priority information to distinguish traffic that should receive different treatment when network resources become constrained. Forwarding classes determine traffic categories and can influence queue selection, while schedulers control transmission behavior. Rewrite mechanisms modify packet markings for downstream devices. Loss priority therefore provides a way to indicate the relative importance of packets with respect to congestion-related dropping. This concept is especially useful when designing differentiated service behavior for traffic with different tolerance levels.

Question 331

Which queue-management technique discards packets before congestion peaks?

1. RED
2. LACP
3. BFD
4. VRRP

Correct Answer: 1

Explanation:

Random Early Detection, commonly called RED, is a queue-management technique that can begin dropping or marking packets before a queue becomes completely full. The objective is to manage congestion more proactively rather than waiting until the queue reaches maximum capacity. Early packet treatment can encourage responsive transport protocols to reduce transmission rates and help avoid severe queue buildup. LACP manages aggregated links, BFD detects forwarding failures, and VRRP provides gateway redundancy. RED therefore belongs to congestion-management and queue-behavior mechanisms within network quality-of-service designs.

Question 332

Which traffic-control mechanism intentionally delays packets to enforce bandwidth?

1. Shaping
2. Filtering
3. Sampling
4. Authentication

Correct Answer: 1

Explanation:

Traffic shaping controls transmission rates by buffering packets and intentionally delaying them when necessary so traffic conforms to a configured rate. Unlike simple packet dropping, shaping attempts to smooth traffic bursts while maintaining a controlled output rate. Filtering determines whether traffic matches specified conditions, sampling collects selected traffic information, and authentication verifies identity or access credentials. Shaping is therefore a traffic-management technique focused on controlling the timing and rate at which packets leave an interface or queue. It can be useful when traffic must conform to contractual or engineered bandwidth limits.

Question 333

Which firewall-filter action silently removes matching packets?

1. Reject
2. Discard
3. Count
4. Log

Correct Answer: 2

Explanation:

The discard action removes matching packets without providing the type of explicit rejection response associated with a reject action. This can be useful when traffic should simply be dropped according to a firewall-filter policy. A count action records matching traffic statistics, while log records information about matching packets for troubleshooting or monitoring purposes. Reject differs because it can generate a response depending on the protocol and configuration. Understanding these actions is important when designing Junos firewall filters because the selected action determines both the packet disposition and any observable response behavior.

Question 334

Which firewall-filter action can generate an explicit rejection response?

1. Count
2. Sample
3. Reject
4. Discard

Correct Answer: 3

Explanation:

The reject action explicitly refuses matching traffic and can generate an appropriate protocol response depending on the traffic type and configuration. This differs from discard, which silently removes the packet. Count is used to maintain statistics about matching traffic, while sample can send selected traffic information to a sampling mechanism. The distinction between reject and discard is particularly important when troubleshooting connectivity because a rejected connection may receive an immediate indication that access was denied. Firewall-filter actions should therefore be selected according to both security requirements and desired network behavior.

Question 335

Which Junos command displays configured system logging destinations?

1. show log
2. show configuration
3. show system users
4. show system storage

Correct Answer: 2

Explanation:

The show configuration command displays the active configuration hierarchy, including configured system logging statements when logging has been configured. Administrators can inspect the relevant system logging hierarchy to identify configured destinations, facilities, severity levels, and related options. The show log command is generally used to view actual log-file contents rather than inspect the configuration that defines logging behavior. User and storage commands address different operational areas. Reviewing configuration is therefore appropriate when the goal is to determine how system logging has been configured rather than simply reading existing messages.

Question 336

Which Junos command displays currently logged-in administrative users?

1. show system users
2. show system uptime
3. show system processes
4. show system storage

Correct Answer: 1

Explanation:

The show system users command provides information about users currently logged into the Junos device. This can be useful when administrators need to determine who is actively connected through management sessions or investigate simultaneous administrative access. Uptime information describes how long the system has been running, process information identifies running system processes, and storage information describes filesystem usage. User-session visibility is especially valuable in environments where multiple administrators manage shared infrastructure. The command can help correlate configuration changes or operational activity with active management sessions.

Question 337

Which Junos command displays filesystem capacity and available storage?

1. show system storage
2. show system users
3. show system uptime
4. show system commit

Correct Answer: 1

Explanation:

The show system storage command provides information about storage utilization on a Junos device. Administrators can use it to identify filesystem capacity, available space, and areas that may be approaching resource limits. Storage monitoring is important because insufficient filesystem capacity can interfere with logging, software installation, core-file creation, or other system operations. User information identifies active management sessions, uptime reports system runtime, and commit information focuses on configuration history. Therefore, storage-related troubleshooting should begin with the command designed to display filesystem resource usage.

Question 338

Which Junos command displays the currently active configuration hierarchy?

1. show system users
2. show configuration
3. show system alarms
4. show route

Correct Answer: 2

Explanation:

The show configuration command displays the configuration currently loaded into the active configuration database. Administrators use it to review configured interfaces, protocols, policies, services, system settings, and other configuration elements. This differs from commands that display operational state such as routing information or system alarms. Reviewing the configuration is often an important first step before making changes because it reveals how the device is currently configured. The command can also be used with additional hierarchy or formatting options when a more focused configuration view is required.

Question 339

Which Junos operation restores configuration from a previous committed version?

1. rollback
2. load merge
3. commit
4. load override

Correct Answer: 1

Explanation:

The rollback operation allows administrators to return the candidate configuration toward a previously committed configuration state. Junos maintains configuration history so that earlier versions can be selected when changes need to be reversed or reviewed. After selecting a rollback version, the resulting candidate configuration should be examined before it is committed. load merge incorporates additional configuration, load override replaces the candidate configuration from an input source, and commit activates the current candidate configuration. Rollback is therefore the Junos mechanism associated with restoring earlier committed configuration content.

Question 340

Which Junos feature applies shared configuration statements across groups?

1. Apply groups
2. Route policies
3. Firewall terms
4. Interface families

Correct Answer: 1

Explanation:

Junos apply groups provide a mechanism for defining reusable configuration statements that can be applied to multiple configuration objects. This can reduce repetitive configuration and make large device configurations easier to maintain. Instead of entering identical statements repeatedly, administrators can define common settings in a group and reference that group where needed. Route policies control routing decisions, firewall terms define packet-filtering behavior, and interface families identify protocol families supported on interfaces. Apply groups therefore focus on configuration reuse and consistency rather than packet forwarding or route selection.