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

 

Question 161

What does the Junos show system uptime command display?

1. Active BGP neighbor table
2. System boot time and load averages
3. Physical interface error counters
4. Total storage disk space utilization

Correct Answer: 2

Explanation

The show system uptime operational command provides network engineers with essential timeline data regarding how long a Junos device has been continuously running since its last restart or power cycle. When invoked, it outputs the current system time, total operational uptime duration, logged-in user counts, and system load average metrics across one, five, and fifteen-minute intervals. Monitoring these load averages is critical for determining whether control plane processors are experiencing undue CPU stress or routine operational stability.

Question 162

Which Mist SLE metric evaluates Wi-Fi client throughput performance?

1. Throughput SLE metric
2. Time-to-connect metric
3. Roaming performance metric
4. AP coverage metric

Correct Answer: 1

Explanation

The Throughput Service Level Expectation metric within the Juniper Mist platform measures and evaluates real-world data rates experienced by wireless clients connected to access points. Instead of merely tracking theoretical maximum link speeds, this metric evaluates actual packet success rates, MCS rates, and channel utilization parameters against predefined thresholds. If client throughput drops below acceptable baselines, the Mist AI engine flags the anomaly, enabling network administrators to isolate interference sources, coverage holes, or faulty client network cards quickly.

Question 163

What is the primary function of an OSPF Area Border Router (ABR)?

1. Translating Type 7 LSAs
2. Connecting multiple OSPF areas
3. Encrypting WAN data links
4. Managing DHCP address pools

Correct Answer: 2

Explanation

An OSPF Area Border Router sits at the boundary connecting one or more OSPF areas to the central backbone area (Area 0). Its primary operational function is to maintain separate link-state databases for each connected area, summarize routing information, and route traffic between disparate areas efficiently. By restricting detailed topology flooding to local areas while propagating summary routes across the ABR, OSPF minimizes routing table sizes and optimizes network convergence performance across enterprise deployments.

Question 164

Which Junos command verifies active BGP peer status?

1. show ospf neighbor
2. show route summary
3. show bgp summary
4. show interface terse

Correct Answer: 3

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 reset issues.

Question 165

What security threat does Port Security mitigate on switch ports?

1. Unauthorized physical MAC addresses
2. Slow wireless roaming latency
3. High CPU temperature spikes
4. Fiber signal loss attenuation

Correct Answer: 1

Explanation

Port security is a robust layer two access control feature that restricts input on switch interfaces by limiting and recording the physical MAC addresses of connected devices. Administrators can configure specific maximum MAC address limits per port. If an unknown device connects or the limit is exceeded, the switch triggers configured violation modes—such as restricting traffic or shutting down the interface—protecting the network from unauthorized endpoint attachments and spoofing attempts.

Question 166

Which protocol is used for gRPC streaming telemetry on Mist switches?

1. SNMP v2c polling
2. Syslog file forwarding
3. NetFlow packet export
4. Protocol buffers

Correct Answer: 4

Explanation

Mist-managed switches utilize modern streaming telemetry mechanisms powered by gRPC and protocol buffers to communicate effectively with the cloud architecture. Unlike traditional polling methods such as SNMP which can introduce high latency and resource overhead, gRPC streaming pushes real-time interface statistics, CPU utilization, and hardware sensor metrics directly to the cloud platform. This enables instantaneous visibility, rapid event correlation, and precise analytics within the Mist dashboard interface without straining switch CPU cycles.

Question 167

What does a flashing green LED indicate on a Mist access point?

1. Hardware initialization fault
2. Firmware upgrade in progress
3. Normal cloud connectivity
4. BLE beacon mode active

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 green indicator typically signals that a firmware upgrade, image download, or configuration synchronization process is currently in progress. 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 168

Which Junos command saves the active configuration as the rescue file?

1. request system rescue save
2. commit rescue baseline
3. save configuration rescue
4. set system rescue-file

Correct Answer: 1

Explanation

The request system rescue save command allows an administrator to store a known, stable configuration file as the official rescue configuration on a Junos device. If an active configuration becomes severely corrupted or locks out management access due to critical operator errors, administrators can instantly revert back to this saved baseline state by executing a simple rollback command or using the boot recovery menu. This ensures that a reliable operational fallback configuration is always preserved independently of standard rolling archive commits.

Question 169

What is the default OSPF hello timer interval on broadcast networks?

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

Correct Answer: 4

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 170

Which feature provides point-to-point Layer 2 encryption on switches?

1. MACsec
2. DHCP Snooping
3. Root Guard
4. Port Security

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 171

What action does a switch take in ‘restrict’ port-security mode?

1. Shuts down the interface
2. Drops traffic and logs event
3. Reboots the control plane
4. Forwards packets silently

Correct Answer: 2

Explanation

When switch port security is configured with the restrict violation mode, the device systematically drops incoming data frames originating from source MAC addresses that exceed the configured maximum learning limit or fail dynamic validation checks. Unlike the alternative shutdown mode which completely disables the physical interface and requires manual administrator intervention, the restrict mode maintains the active link status of the port while simultaneously generating an administrative syslog message and incrementing internal violation security counters.

Question 172

Which BGP attribute is evaluated first during route selection?

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

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 173

What is the core function of Mist Marvis AI assistant?

1. Optical fiber cable testing
2. Automated troubleshooting analytics
3. Battery backup power monitoring
4. Static VLAN provisioning

Correct Answer: 2

Explanation

Mist Marvis functions as the core virtual network assistant powered by advanced artificial intelligence and sophisticated machine learning algorithms designed specifically for modern enterprise environments. Its primary operational function is to continuously analyze live streaming telemetry data, correlate multi-domain network events, and translate complex infrastructure health metrics into clear, actionable troubleshooting steps. By fully automating root cause analysis workflows across wireless, wired, and security layers, Marvis significantly reduces mean time to resolution and minimizes administrative overhead.

Question 174

Which command displays hardware inventory on a Junos device?

1. show chassis hardware
2. show system memory
3. show route summary
4. show ethernet switching

Correct Answer: 1

Explanation

The show chassis hardware command provides a comprehensive, itemized inventory list of all physical hardware components installed within a Junos routing or switching platform. It outputs exact model numbers, serial numbers, and physical descriptions for power supplies, fan trays, routing engines, interface modules, and line cards. This command is invaluable for network engineers during asset management tracking, warranty verification, hardware inventory audits, and physical troubleshooting sessions.

Question 175

What is the primary benefit of deploying a Juniper Virtual Chassis?

1. Increasing fiber optic lengths
2. Unifying control planes and resilience
3. Encrypting Wi-Fi management frames
4. Converting copper to wireless signals

Correct Answer: 2

Explanation

Virtual Chassis technology allows multiple interconnected EX Series switches to function as a single unified logical device, significantly simplifying network management and topology design. Instead of managing individual switch IP addresses and configuration files separately, administrators interact with a single control plane across the stack. This architecture provides high availability through distributed link aggregation groups, seamless failover mechanisms, and simplified spanning tree topologies by eliminating bridge loops.

Question 176

Which standard defines Rapid Spanning Tree Protocol convergence?

1. IEEE 802.1Q
2. IEEE 802.3ad
3. IEEE 802.1X
4. IEEE 802.1w

Correct Answer: 4

Explanation

Rapid Spanning Tree Protocol is standardized globally under IEEE 802.1w, offering significant convergence speed improvements over legacy IEEE 802.1D bridging standards. RSTP introduces explicit proposal-agreement handshakes between neighboring switches, allowing designated and root ports to transition directly into forwarding states almost instantaneously when link changes occur. This eliminates lengthy listening and learning delays, preventing broadcast storms and bridge loops while maintaining uninterrupted application session uptime.

Question 177

What database repository does Dynamic ARP Inspection utilize?

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

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 178

Which Junos command discards uncommitted candidate configuration changes?

1. rollback zero
2. discard changes
3. clear candidate
4. exit abandon

Correct Answer: 2

Explanation

In Junos OS, the discard changes command is used within configuration mode to abandon any pending modifications made to the active candidate configuration database without applying them. This is an essential safety feature when an administrator tests complex configuration scenarios or makes inadvertent syntax edits and wishes to revert the candidate database back to the exact state of the current running configuration. Once executed, the editor discards the staging buffer and preserves system stability.

Question 179

What role does Mist Edge serve in remote branch network architectures?

1. Local web cache storage
2. Firewall packet inspection
3. Tunnel aggregation and steering
4. DHCP server address leasing

Correct Answer: 3

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 180

Which command verifies active OSPF neighbor adjacencies?

1. show bgp summary
2. show route protocol ospf
3. show interface terse
4. show ospf neighbor

Correct Answer: 4

Explanation

The show ospf neighbor command serves as the primary operational tool utilized by network engineers to inspect the live, real-time status of OSPF neighbor adjacencies across routing topologies. When executed, this command outputs critical runtime metrics including remote neighbor router IDs, current protocol progression states such as Full or 2-Way, local interface designations, and active dead timer countdown intervals. Verifying this operational output enables administrators to quickly diagnose and isolate routing protocol stuck states.