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

 

Question 101

Which two primary configuration databases does Junos OS utilize for managing system settings?

1. Startup and Running databases
2. Candidate and Running databases
3. Active and Backup databases
4. Local and Remote databases

Correct Answer: 2

Explanation

Junos OS maintains a strict separation between the candidate configuration and the running configuration databases. The candidate configuration serves as an isolated staging buffer where administrators can make, edit, and test configuration modifications safely without impacting the active production environment. This prevents accidental syntax errors or disruptive changes from breaking network services immediately. Once edits are verified and approved, executing a commit command applies the candidate changes to the active running database, ensuring robust operational stability and safe administrative control.

Question 102

What specific switch conditions does Mist Wired Assurance primarily monitor to detect anomalies?

1. Port flaps, cabling faults, and duplex mismatches
2. Satellite signal strength and atmospheric attenuation
3. Battery charge levels on peripheral devices
4. Bluetooth beacon proximity metrics

Correct Answer: 1

Explanation

Mist Wired Assurance leverages advanced artificial intelligence and cloud telemetry to continuously analyze switch metrics and identify hardware anomalies instantly. It monitors critical layer two parameters such as physical port flaps, cabling faults, duplex mismatches, and power over health status. By applying machine learning to these telemetry streams, the platform detects physical infrastructure issues before they impact end-user experience, drastically reducing mean time to resolution for enterprise network support teams.

Question 103

What primary metric determines the Master routing engine election in a Juniper Virtual Chassis?

1. Lowest physical MAC address value
2. Configured routing engine priority value
3. Total number of member switch ports
4. Sequential switch serial number order

Correct Answer: 2

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, generating unified configuration databases, and synchronizing routing tables across the stack. 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 104

What is the default OSPF hello timer interval on multi-access broadcast network segments?

1. 10 seconds
2. 30 seconds
3. 60 seconds
4. 5 seconds

Correct Answer: 1

Explanation

Open Shortest Path First utilizes hello packets to discover neighboring routers, establish adjacencies, and monitor link health across the network topology. On standard multi-access broadcast and point-to-point links, the default OSPF hello timer interval is set to 10 seconds, with a corresponding dead timer interval of 40 seconds. Ensuring consistent timer configurations across interconnected routers is critical; any mismatch in hello or dead intervals will prevent neighbor adjacencies from forming successfully.

Question 105

Which action modifiers are available when defining firewall filters on Juniper EX Series switches?

1. Encrypt and Compress
2. Route-Cache and Translate
3. Accept and Discard
4. Bridge and Route

Correct Answer: 3

Explanation

Junos firewall filters provide granular, hardware-accelerated packet inspection capabilities on Juniper EX Series switches, allowing administrators to match traffic based on layer two, layer three, and layer four parameters. When traffic matches specified filter criteria, administrators can apply terminal action modifiers such as accept to permit the traffic, or discard / reject to drop unauthorized packets instantly. This capability is vital for mitigating denial-of-service attacks, enforcing departmental security isolation, and protecting management plane interfaces.

Question 106

What is the primary function of the BGP AS-Path attribute during path selection?

1. Preventing routing loops and determining path preference
2. Calculating physical interface bandwidth availability
3. Encrypting data frames across public WAN circuits
4. Assigning dynamic VLAN tags to untrusted endpoints

Correct Answer: 1

Explanation

The Border Gateway Protocol AS-Path attribute is a mandatory well-known transitive attribute that records every autonomous system number a route announcement traverses. During route selection, BGP favors routes with the shortest AS-Path length, as fewer transit hops generally translate to lower latency. Furthermore, routers use the AS-Path attribute for robust loop prevention; if a router receives an update containing its own autonomous system number within the AS-Path list, it rejects the route immediately to prevent routing loops.

Question 107

Which Mist Service Level Expectation metric specifically evaluates wireless authentication performance?

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

Correct Answer: 4

Explanation

Service Level Expectations serve as the essential foundation for measuring actual user experience within the modern Mist architecture. The time-to-connect SLE metric specifically tracks client onboarding performance, including association, authentication duration, and DHCP IP address acquisition success rates. By continuously evaluating authentication metrics against predefined baselines, network administrators can instantly identify whether users are experiencing satisfactory onboarding performance or encountering specific security handshake failures across the wireless network infrastructure.

Question 108

Which operational command allows administrators to view active system alarms on a Junos device?

1. show route summary
2. show system alarms
3. show interface terse
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.

Question 109

What does a flashing amber LED status indicator typically signify on a Juniper Mist access point?

1. Normal cloud-connected operational status
2. Firmware download or bootloader status in progress
3. Active Bluetooth Low Energy tracking beacon mode
4. Power over Ethernet wattage overload condition

Correct Answer: 2

Explanation

On Juniper Mist access points, integrated multi-color LED status indicators provide immediate visual feedback regarding the operational health and activity state of the hardware. A flashing amber or yellow indicator typically signals that a firmware upgrade, image download, or bootloader status process is currently active. This visual cue alerts engineers that the access point is actively processing software updates and should not be powered off or disconnected from the network until the sequence completes successfully.

Question 110

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

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

Correct Answer: 1

Explanation

Dynamic ARP Inspection is a 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. This protects the local network segment from spoofing attacks.

Question 111

What is the primary operational purpose of configuring a routing instance of type virtual-router?

1. Layer 2 Ethernet bridging across access ports
2. Non-forwarding out-of-band management control
3. Complete IP routing table isolation and multi-tenancy
4. Wireless radio resource management tuning

Correct Answer: 3

Explanation

Virtual routing instances enable a single physical Juniper routing or switching device to maintain multiple isolated virtual routing tables simultaneously. Each routing instance operates independently, allowing overlapping IP address spaces and distinct routing protocol configurations to coexist securely on the same hardware platform. This is widely implemented in enterprise multi-tenancy designs, security segmentation projects, and data center edge connectivity, where traffic separation between different departments or external clients is mandatory for compliance and operational isolation.

Question 112

What action does the Junos command clear system rollback perform?

1. Reboots the physical routing engine hardware
2. Deletes historical rollback configuration files
3. Resets all interface traffic counter statistics
4. Clears uncommitted candidate configurations

Correct Answer: 2

Explanation

The Junos clear system rollback command allows administrators to purge historical rollback configuration files stored in the system archive directory. By default, Junos preserves up to fifty historical rollback files indexed numerically. Executing this cleanup command removes older archival versions to free up system storage space or comply with administrative retention policies, while leaving the current running and rescue configurations completely untouched and secure.

Question 113

Which protocol provides automatic neighbor discovery and address resolution for IPv6 networks?

1. ICMPv6 Neighbor Discovery
2. Address Resolution Protocol ARP
3. Dynamic Host Configuration Protocol
4. OSPF version 2 link-state

Correct Answer: 1

Explanation

In IPv6 network architectures, traditional ARP is replaced entirely by ICMPv6 Neighbor Discovery protocols. Neighbor Discovery handles core functions including router solicitation, router advertisement, neighbor solicitation, neighbor advertisement, and duplicate address detection. By utilizing multicast messaging and ICMPv6 frame structures, nodes discover local link-layer addresses and verify network reachability dynamically without requiring broadcast-based ARP requests common in legacy IPv4 environments.

Question 114

What specific threat does Spanning Tree Root Guard prevent in enterprise switching networks?

1. Rogue switches taking over the root bridge role
2. Unauthenticated wireless client association attempts
3. High-frequency broadcast storm generation
4. Physical cable signal attenuation issues

Correct Answer: 1

Explanation

Spanning Tree Root Guard is an essential security feature configured on designated ports to ensure that the primary root bridge remains authoritative across the enterprise switching topology. If a rogue switch connects to a port enabled with Root Guard and transmits superior superior bridge protocol data units attempting to become the root bridge, the switch transitions the port into a root-inconsistent blocking state. This prevents malicious or misconfigured devices from altering the spanning tree topology and disrupting traffic paths.

Question 115

What system metrics does the Junos operational command show system storage display?

1. Active BGP routing table prefix counts
2. Flash disk space utilization across partitions
3. Switch CPU core cache performance data
4. Transceiver optical power receive levels

Correct Answer: 2

Explanation

The show system storage command provides a detailed breakdown of disk space utilization across all internal flash partitions, storage drives, and mounted file systems on a Junos device. When executed, it outputs total capacity, used space, available percentages, and mount point directories. Monitoring storage utilization is critical for ensuring that system log files, core dumps, and software installation images do not exhaust available disk space, which could otherwise lead to system instability.

Question 116

What is the primary benefit of deploying site templates within the Juniper Mist cloud management platform?

1. Managing physical fiber cable installation lengths
2. Ensuring global configuration consistency across multiple locations
3. Providing manual radio frequency channel tuning
4. Storing local switch operating system images

Correct Answer: 2

Explanation

Site templates in the Juniper Mist platform empower network administrators to define standardized configuration policies—including VLANs, firewall rules, Wi-Fi SSIDs, and switch profiles—at a global level and push them seamlessly across hundreds of remote branch locations. This eliminates repetitive manual configurations, ensures strict compliance and policy consistency across the entire enterprise enterprise footprint, and simplifies day-two operational management as new sites are provisioned onto the network.

Question 117

What does an OSPF database adjacency state of Init signify between two connected routers?

1. Complete link-state database synchronization
2. Hello packet received but router ID missing in neighbor list
3. Adjacency fully established and routing active
4. Dead timer interval expired completely

Correct Answer: 2

Explanation

An OSPF adjacency state of Init indicates that the local router has received a hello packet from a neighbor router, but its own router ID was not included within the neighbor field of the incoming packet. This confirms that one-way communication exists, but bidirectional communication has not yet been established. The neighbor router must acknowledge the local router’s hello packet before the adjacency can transition into the 2-Way state.

Question 118

Which operational command displays active Border Gateway Protocol summary statistics on a Junos device?

1. show bgp summary
2. show ospf interface
3. show route table
4. show chassis routing-engine

Correct Answer: 1

Explanation

The show bgp summary command is the essential operational tool utilized by network engineers to inspect the live status, session states, and prefix advertisement statistics of all configured Border Gateway Protocol peers. When executed on a Junos routing platform, it outputs critical runtime details including remote peer IP addresses, autonomous system numbers, active connection states, and the total number of prefixes received from each peer. Verifying this output allows administrators to quickly identify peer flapping or session resets.

Question 119

What operational benefit do Port Fast or Edge Port features provide in Layer 2 switching topologies?

1. Delaying port forwarding states by thirty seconds
2. Bypassing listening and learning states for access ports
3. Encrypting all layer two user data payloads
4. Preventing unknown multicast traffic storms

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 120

What system health parameters does the show chassis routing-engine command output on a Junos device?

1. CPU, memory utilization, and system uptime metrics
2. Active BGP peer summary state tables
3. Physical interface error counters and CRC drops
4. Dynamic ARP inspection binding table records

Correct Answer: 1

Explanation

The show chassis routing-engine command provides critical health and performance metrics for the control plane processor on a Junos platform. When executed, it outputs current CPU utilization percentages, system memory usage statistics, temperature sensor readings, system boot uptime, and routing engine load averages. Monitoring this command is essential for diagnosing control plane congestion, high CPU utilization caused by routing protocol churn, or resource bottlenecks impacting management access.