View Full Juniper JN0-253 Exam Dumps and Practice Test Dumps.

 

Question 201

What do the numbers represent in the Junos physical interface name ge-0/1/2?

1. Failsafe channel, routing engine, and port
2. FPC slot, PIC slot, and port number
3. VLAN ID, switch block, and core link
4. Autonomous system, area, and router ID

Correct Answer: 2

Explanation

Junos OS utilizes a standardized hierarchical naming convention for physical and logical interfaces. In the interface name ge-0/1/2, the first number (0) represents the Flexible PIC Concentrator slot, the middle number (1) indicates the Physical Interface Card slot, and the final number (2) specifies the individual port number on that card. The prefix (ge) denotes Gigabit Ethernet capability. This modular naming scheme remains consistent across diverse Juniper routing and switching platforms.

Question 202

What primary operational benefit does Juniper Mist WAN Assurance provide?

1. AI-driven insights and visibility for WAN and SD-WAN
2. Automated physical fiber optic cable splicing
3. Manual packet capture script generation
4. Local battery backup power regulation

Correct Answer: 1

Explanation

Juniper Mist WAN Assurance extends the power of cloud-native artificial intelligence and machine learning to wide area network operations. By leveraging rich telemetry data collected from edge devices, it provides deep visibility into user experience, application performance, and transport link health. Mist WAN Assurance automates event correlation, simplifies root cause analysis, and detects anomalies across SD-WAN fabrics, significantly reducing troubleshooting times and ensuring optimal application delivery across enterprise branch locations.

Question 203

Which OSPF parameter takes precedence when electing a Designated Router on a broadcast network segment?

1. Lowest MAC address assigned to the interface
2. Highest OSPF interface priority value
3. Shortest static default route metric
4. Highest loopback IP address assigned

Correct Answer: 2

Explanation

When OSPF routers establish adjacencies on a multi-access broadcast network, they conduct a Designated Router and Backup Designated Router election process. The primary parameter evaluated during this election is the OSPF interface priority value configured on each router interface; the router with the highest numerical priority wins. If priorities are tied, the router with the highest OSPF Router ID is selected as the DR. Setting priority to zero ensures a router never participates in the election.

Question 204

Which attribute is evaluated before AS-Path length during standard BGP path selection?

1. Multi-Exit Discriminator
2. Origin code type
3. Local Preference value
4. Router ID value

Correct Answer: 3

Explanation

Border Gateway Protocol evaluates a strict sequence of attributes to determine the best path to a destination prefix when multiple routes exist. The Local Preference attribute is evaluated first among externally learned routes; a higher Local Preference value is always preferred. This attribute is exchanged internally within an autonomous system, allowing network administrators to dictate outbound exit points and traffic engineering policies across enterprise edge routers before examining AS-Path lengths or other tie-breaking metrics.

Question 205

What occurs on an untrusted port when DHCP Snooping intercepts an unauthorized DHCP server offer message?

1. The packet is dropped immediately
2. The packet is encrypted using MACsec
3. The interface is converted to a trunk port
4. The router ID is reset to default

Correct Answer: 1

Explanation

When DHCP Snooping is enabled, switch ports are designated as either trusted or untrusted. Untrusted ports face client endpoints and are strictly prohibited from originating server-side DHCP responses. If an unauthorized rogue device connected to an untrusted port attempts to send DHCP offer or acknowledgment packets, the switch intercepts and drops those frames immediately. This security mechanism protects enterprise clients from IP spoofing and rogue gateway attacks.

Question 206

Which RSTP port role is defined as a backup path to the root bridge if the primary root port fails?

1. Designated port
2. Alternate port
3. Master port
4. Disabled port

Correct Answer: 2

Explanation

Under Rapid Spanning Tree Protocol, the alternate port role represents a port that receives superior BPDU information from another switch but is blocked because it is not the chosen path to the root bridge. If the primary root port on a switch experiences a physical link failure, the alternate port transitions immediately into the root port forwarding state without enduring legacy listening and learning delays. This rapid transition mechanism ensures minimal application downtime during topology reconvergence.

Question 207

How is the Master routing engine determined in a newly deployed Juniper Virtual Chassis?

1. Lowest MAC address among member switches
2. Random selection during initialization
3. Highest configured member priority and election tie-breakers
4. First physical switch powered on in the rack

Correct Answer: 3

Explanation

When a Juniper Virtual Chassis initializes, member switches participate in an automated master election process to determine which switch controls the shared control plane. The election evaluates configured routing engine member priorities first; the switch with the highest priority value is selected as the Master. If priorities match, additional tie-breakers such as member slot IDs or serial numbers are evaluated. This process ensures a deterministic, predictable master assignment across stacked EX Series switches.

Question 208

Which command reverts the active Junos configuration to a specific historical index, such as rollback 3?

1. rollback 3
2. reset configuration index 3
3. restore archive 3
4. undo changes 3

Correct Answer: 1

Explanation

The Junos rollback command allows administrators to instantly revert the active candidate configuration to any previously committed configuration stored in the system archives. Junos automatically maintains up to fifty historical rollback files, indexed numerically from zero up to forty-nine. By specifying a rollback index number (e.g., rollback 3), engineers can quickly undo recent configuration errors or restore known good operating states without manually retyping configuration hierarchies.

Question 209

What security risk does Dynamic ARP Inspection protect against?

1. Man-in-the-middle ARP spoofing attacks
2. High-frequency broadcast storms
3. Wireless client roaming latency
4. CPU temperature overheating

Correct Answer: 1

Explanation

Dynamic ARP Inspection is a robust layer two security feature that leverages valid bindings stored within the DHCP snooping database to intercept, inspect, and drop malicious ARP packets. In typical enterprise networks, attackers attempt man-in-the-middle attacks by poisoning ARP caches with forged address bindings, tricking devices into sending traffic to unauthorized MAC addresses. DAI validates every untrusted ARP packet against verified IP-to-MAC bindings, discarding anomalous or conflicting frames immediately.

Question 210

What is the primary role of Marvis Actions within the Juniper Mist architecture?

1. Translating Type 7 OSPF LSAs
2. Providing proactive recommendations and automated root cause analysis
3. Encrypting physical data center fiber links
4. Generating static routing table entries

Correct Answer: 2

Explanation

Marvis Actions serves as the intelligent core of the Juniper Mist platform, utilizing advanced machine learning algorithms to translate complex streaming telemetry data into clear, actionable recommendations. Instead of forcing engineers to manually sift through logs and event counters, Marvis Actions identifies the exact root cause of network faults—ranging from DHCP failures and bad cables to authentication timeouts and coverage holes—and delivers precise remediation steps to streamline enterprise IT operations.

Question 211

Which prompt symbol indicates that a Junos device is currently in operational monitoring mode?

1. Hash pound symbol (#)
2. Greater-than sign (>)
3. Percent sign (%)
4. Dollar sign ($)

Correct Answer: 2

Explanation

Junos OS utilizes distinct prompt indicators to inform administrators which CLI mode is currently active. The operational monitoring mode prompt always ends with the greater-than sign (>), indicating that the user has read-only access to monitoring commands, statistics, ping diagnostics, and system health checks. Conversely, when an administrator enters configuration mode via the edit command, the prompt transitions to end with a hash pound symbol (#).

Question 212

Which OSPF area type prevents the flooding of external Type 5 LSAs and uses a default summary route instead?

1. Stub area
2. Backbone area
3. Transit area
4. Not-So-Stubby area

Correct Answer: 1

Explanation

An OSPF stub area is a specialized area design that blocks the propagation of external AS-type routing updates originating from outside the OSPF autonomous system. Instead of maintaining resource-heavy external routing tables, internal routers within a stub area receive a default summary route from the Area Border Router to reach external destinations. This optimization significantly reduces routing table memory footprints, lowers CPU utilization, and improves protocol stability across remote branch office routers.

Question 213

At which OSI layer does MACsec provide point-to-point data encryption and integrity?

1. Layer 3 Network layer
2. Layer 2 Data Link layer
3. Layer 4 Transport layer
4. Layer 7 Application layer

Correct Answer: 2

Explanation

MACsec, standardized under IEEE 802.1AE, provides point-to-point data encryption, data integrity, and data origin authenticity at Layer 2 of the OSI model. By securing Ethernet links between switches or client endpoints, MACsec protects against man-in-the-middle wiretapping, MAC tampering, and passive eavesdropping attacks. It encrypts traffic transparently across physical cabling without altering higher-layer routing protocols, making it an essential security standard for sensitive campus backbones.

Question 214

What mode must at least one peer switch be configured with for an LACP link aggregation bundle to form successfully?

1. Passive mode
2. Active mode
3. Disabled mode
4. Static-only mode

Correct Answer: 2

Explanation

Link Aggregation Control Protocol defines specific operational modes for member interfaces to govern how control packets are exchanged. An interface configured in active mode actively initiates LACP negotiation by transmitting protocol frames, whereas a passive mode interface responds to incoming LACP frames but does not initiate them. For an LACP bundle to form successfully, at least one peer device must be configured in active mode; if both peers are set to passive, LACP packets are never initiated.

Question 215

What primary technological advantage do gRPC streaming telemetry protocols offer over traditional SNMP polling?

1. Complete encryption of all physical copper cables
2. Real-time data streaming with significantly lower CPU overhead
3. Automated conversion of Layer 2 frames to Layer 7 apps
4. Elimination of routing protocol neighbor timers

Correct Answer: 2

Explanation

Streaming telemetry powered by gRPC and protocol buffers offers massive operational advantages over legacy SNMP polling methods. Traditional SNMP requires periodic polling intervals that consume switch CPU cycles and introduce data latency. In contrast, gRPC streaming pushes real-time interface statistics, hardware sensor metrics, and operational counters directly to management platforms on a change-of-state basis. This enables instantaneous visibility and precise analytics without straining switch control plane resources.

Question 216

What happens if an administrator fails to confirm a configuration change after executing the commit confirmed command within the specified timeout?

1. The device reboots instantly into ROM monitor mode
2. The configuration automatically rolls back to the previous stable state
3. The candidate configuration is permanently erased from flash
4. All physical interfaces are permanently shut down

Correct Answer: 2

Explanation

The commit confirmed command in Junos OS is a critical safety mechanism designed to prevent network engineers from locking themselves out of remote devices due to erroneous configuration changes. When executed, the device applies the configuration temporarily while starting a countdown timer. If the administrator loses network connectivity and fails to verify the changes with a standard commit command before the timer expires, Junos automatically rolls back the configuration to the previous stable state, restoring management access instantly.

Question 217

Which Mist Service Level Expectation metric tracks wireless onboarding success and authentication speed?

1. Time-to-Connect SLE metric
2. Roaming performance SLE metric
3. Throughput SLE metric
4. Coverage SLE metric

Correct Answer: 1

Explanation

The Time-to-Connect Service Level Expectation metric within the Juniper Mist platform evaluates the overall client onboarding experience by breaking down association, authentication, and DHCP acquisition phases. It measures latency and failure rates for each step, allowing network engineers to instantly isolate whether connection bottlenecks stem from slow RADIUS servers, DHCP pool starvation, or wireless authentication timeouts. This granular tracking shifts troubleshooting focus from infrastructure uptime to true end-user connectivity health.

Question 218

What action does a switch port configured with port-security violation protect mode take upon receiving an unauthorized MAC address?

1. Shuts down the port
2. Drops traffic silently without generating syslog messages
3. Drops traffic and logs syslog alerts
4. Translates the source address

Correct Answer: 2

Explanation

When port security is configured with the protect violation mode, the switch drops incoming frames from unauthorized MAC addresses that exceed configured limits without disrupting traffic from authorized endpoints. Unlike the restrict mode which logs syslog messages and increments security violation counters, the protect mode drops traffic silently without generating operational logs or alert notifications. This mode is typically deployed in high-security environments where silent mitigation of rogue devices is preferred.

Question 219

What is the primary function of Mist Edge in distributed campus and remote branch architectures?

1. Tunnel aggregation and traffic steering
2. Local web server proxy caching
3. Dynamic OSPF route calculation
4. Core database hardware replication

Correct Answer: 1

Explanation

Mist Edge is expertly engineered to extend corporate campus fabrics and provide distributed tunnel aggregation capabilities for remote access point deployments. It terminates secure IPsec or GRE tunnels originating from remote branch access point deployments right back to the central datacenter or enterprise campus edge. This allows network administrators to maintain centralized tunneling policies, dynamic VLAN mapping, and secure traffic steering while still leveraging decentralized wireless architectures across various branch offices seamlessly.

Question 220

Which Junos operational command displays active system alarms and hardware warnings?

1. show route summary
2. show system alarms
3. show interface extensive
4. show ospf neighbor

Correct Answer: 2

Explanation

The show system alarms command provides an immediate operational overview of active hardware faults, software daemon errors, and environmental warnings on a Junos routing or switching platform. When executed, it categorizes alarms by severity, detailing issues such as power supply failures, fan tray faults, high CPU utilization, or temperature threshold breaches. Monitoring this output allows network engineers to detect critical hardware degradation and initiate proactive maintenance before system stability is compromised.