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

 

Question 181

What operational purpose does the Junos rollback command serve?

1. Reboots routing hardware
2. Reverts configuration changes
3. Clears interface counters
4. Erases flash storage

Correct Answer: 2

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, engineers can quickly undo recent configuration errors or restore known good operating states without manually retyping configuration hierarchies. This archive system guarantees rapid recovery from operational mistakes and ensures high network availability.

Question 182

Which platform feature provides automated AI-driven anomaly detection for wired switches?

1. Mist Wired Assurance
2. Local Syslog Viewer
3. SNMP Polling Engine
4. CLI Packet Analyzer

Correct Answer: 1

Explanation

Mist Wired Assurance integrates artificial intelligence and cloud management capabilities directly into the enterprise wired LAN infrastructure. Its core operational purpose is to streamline day-two switch operations, automate device provisioning through reusable templates, and stream rich telemetry data directly to the cloud platform. By applying AI-driven insights to switch metrics, it detects configuration mistakes, port anomalies, cabling faults, and duplex mismatches instantly, ensuring optimal performance and consistent policy enforcement across the network.

Question 183

What database synchronization state follows the Exchange state in OSPF adjacency establishment?

1. Down state
2. Loading state
3. Init state
4. 2-Way state

Correct Answer: 2

Explanation

During OSPF adjacency formation, routers progress through several distinct operational states before achieving full synchronization. After exchanging Database Description packets during the Exchange state, routers transition into the Loading state. In this phase, routers send Link-State Request packets to obtain missing or more detailed link-state records from their neighbors. Once all requested database entries are received and processed, the adjacency successfully transitions into the Full state, indicating complete topological synchronization across the routing domain.

Question 184

Which BGP attribute functions as an optional non-transitive metric for influencing inbound traffic preference?

1. Local Preference
2. AS-Path length
3. Multi-Exit Discriminator
4. Origin code type

Correct Answer: 3

Explanation

The Multi-Exit Discriminator attribute is an optional non-transitive BGP path attribute utilized to inform neighboring autonomous systems of the preferred entry point into the local AS. A lower MED value is preferred during path selection when multiple entry links exist between two autonomous systems. Because it is non-transitive, routers receiving the MED value do not pass it along to subsequent autonomous systems, making it a localized tool for tuning inbound traffic flows efficiently.

Question 185

What operational behavior does a Spanning Tree Port Fast enabled port exhibit upon link-up?

1. Enters listening state for 15 seconds
2. Transitions to forwarding state immediately
3. Blocks all broadcast frames permanently
4. Negotiates trunk encapsulation modes

Correct Answer: 2

Explanation

Port Fast or Edge Port features allow switch access ports connected directly to end-user workstations or servers to transition immediately from blocking to forwarding states, bypassing the traditional listening and learning phases of spanning tree protocols. This eliminates long client onboarding delays and prevents DHCP timeout issues when devices boot up or dock to the network. While edge ports bypass standard STP convergence delays, they still process bridge protocol data units to protect against accidental loops.

Question 186

What specific safety function does a Junos rescue configuration provide?

1. Staging candidate modifications safely
2. Providing a reliable fallback recovery baseline
3. Encrypting system configuration files
4. Updating software images automatically

Correct Answer: 2

Explanation

The rescue configuration serves as an official, trusted backup configuration file that administrators can save explicitly on a Junos device. If an active configuration becomes severely corrupted or operator errors result in total remote management lockout, administrators can instantly revert back to this saved baseline state without needing complex physical intervention or manual configuration reconstruction. This ensures that a reliable operational fallback configuration is always preserved independently of rolling archive commits.

Question 187

What database repository does Dynamic ARP Inspection query to validate packet bindings?

1. DHCP Snooping binding database
2. OSPF link-state routing database
3. Virtual Chassis topology map
4. BGP autonomous system routing table

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 188

How does the Mist Marvis assistant interact with network engineers for troubleshooting?

1. Through a conversational natural language interface
2. By executing manual CLI command scripts
3. Through automated hardware replacement shipping
4. By running offline cable continuity tests

Correct Answer: 1

Explanation

The Marvis Actions framework revolutionizes network management by incorporating a conversational interface that interprets natural language queries from engineers. Users can ask complex questions regarding client connectivity, switch health, or firmware statuses in plain English, and Marvis responds with precise diagnostic details and clear remediation steps. This conversational capability bridges the gap between complex network telemetry data and fast administrative decision-making across enterprise environments without requiring steep learning curves.

Question 189

What role does the switch with the second-highest routing engine priority assume in a Virtual Chassis?

1. Backup routing engine role
2. Secondary standalone gateway
3. Passive uplink switch role
4. Unmanaged slave member role

Correct Answer: 1

Explanation

Within a Juniper Virtual Chassis architecture, member switches are assigned specific operational roles to manage the combined logical entity efficiently. The switch configured with the highest routing engine priority value assumes the Master role, taking charge of the shared control plane and synchronization. The switch with the second-highest priority automatically assumes the Backup role to ensure seamless, hitless failover capabilities if the primary Master switch encounters a hardware failure or reboot event.

Question 190

How do trusted ports process DHCP server response messages when DHCP Snooping is enabled?

1. Dropping all packets silently
2. Forwarding traffic without restriction
3. Encrypting payloads with IPsec
4. Converting frames to Layer 3

Correct Answer: 2

Explanation

When configuring DHCP Snooping on enterprise access switches, network administrators must explicitly define which switch ports connect to legitimate corporate DHCP servers as trusted ports. All other user-facing access ports default to untrusted status. Trusted ports are permitted to forward all DHCP server response messages—including offers and acknowledgments—downstream to legitimate clients, whereas untrusted ports have incoming server-side packets blocked instantly to protect the network from rogue servers.

Question 191

What terminal prompt character indicates that a Junos device is in configuration edit mode?

1. The greater-than sign (>)
2. The hash pound symbol (#)
3. The percent sign (%)
4. The 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 read-only access to statistics and health checks. Conversely, when an administrator enters configuration mode via the edit command, the prompt transitions to end with a hash pound symbol (#), signaling that candidate configuration modifications and staging buffers are fully enabled.

Question 192

What is a primary characteristic of an OSPF Stub Area?

1. Injection of external Type 5 LSAs
2. Replacement of external routes with default route
3. Elimination of all internal routers
4. Disabled neighbor hello timer intervals

Correct Answer: 2

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 193

What operational state configuration allows LACP negotiation to succeed between two switches?

1. Passive mode on both peers
2. Active mode on at least one peer
3. Disabled control protocols
4. Static pin-down assignment

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 194

Which OSI layer does MACsec encryption operate on to protect Ethernet links?

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

Correct Answer: 1

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 and data center interconnects.

Question 195

What security purpose does the Junos commit confirmed command serve?

1. Permanent flash memory overwrite
2. Preventing remote management network lockouts
3. Encrypting candidate configuration files
4. Rebooting the control plane processor

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 196

What feature enables Mist access points to deliver precise indoor location tracking?

1. Multi-element Bluetooth Low Energy array
2. High-frequency radar scanning units
3. Ultrasonic audio receiver beacons
4. GPS satellite triangulation modules

Correct Answer: 1

Explanation

Mist access points feature a patented multi-element Bluetooth Low Energy antenna array that enables highly accurate indoor location services and asset tracking. Unlike traditional single-antenna Bluetooth solutions, the virtual BLE array listens to beacons from client devices and computes precise locations using advanced machine learning algorithms. This capability supports proximity messaging, asset tracking, and indoor wayfinding without requiring dedicated hardware location overlay beacons or complicated physical site calibrations.

Question 197

How does BGP utilize the AS-Path attribute to prevent routing loops?

1. By dropping updates containing its own ASN
2. By calculating physical link bandwidth costs
3. By encrypting route advertisement payloads
4. By rejecting routes with low preference values

Correct Answer: 1

Explanation

The Border Gateway Protocol AS-Path attribute serves as a robust loop prevention mechanism across autonomous systems. When a BGP router receives a route update announcement, it inspects the AS-Path sequence; if the update contains its own autonomous system number listed within the path string, the router rejects and drops the route immediately. This foolproof rule ensures that routing loops cannot persist across interconnected BGP peering domains.

Question 198

Which operational command displays active system alarms and hardware faults on Junos?

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

Correct Answer: 1

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.

Question 199

What is a major architectural benefit of cloud-native access points?

1. Requirement for local hardware controllers
2. Elimination of on-premises controllers
3. Static manual RF channel configuration
4. Local flash log storage limitations

Correct Answer: 2

Explanation

Cloud-native access points are engineered from the ground up to interface directly with scalable cloud management platforms, bypassing the need for traditional on-premises hardware controllers or physical appliances. They offload control plane intelligence, analytics collection, and machine learning computations directly to the cloud. This modern architecture ensures seamless scalability, automated zero-touch provisioning, rapid software updates, and instant global access to telemetry databases without complex local management hierarchies.

Question 200

What role does the candidate configuration play during Junos configuration management?

1. Staging edits safely before commit
2. Overwriting flash memory instantly
3. Disabling all physical switch ports
4. Rebooting the routing engine hardware

Correct Answer: 1

Explanation

In Junos OS, the candidate configuration acts as a secure staging buffer where administrators can make, edit, and test configuration modifications without affecting the active production environment. This isolated workspace prevents accidental syntax errors or disruptive changes from breaking ongoing network operations. Once edits are verified, executing a commit command applies the candidate changes to the active running database, ensuring robust operational stability and safe administrative control.