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

 

Question 341

Which Junos operational command allows an administrator to directly compare the differences between the current candidate configuration and a specific historical rollback file?

1. show configuration candidate
2. show configuration rollback
3. show system rescue diff
4. show running configuration changes

Correct Answer: 2

Explanation

The show configuration rollback command (typically appended with a specific rollback index number like show configuration rollback 1) is an indispensable diagnostic utility in Junos OS. When executed, it generates a side-by-side text comparison highlighting exact additions, modifications, and deletions between the active candidate configuration buffer and the designated historical rollback checkpoint. This allows network administrators to carefully audit experimental changes, trace syntax adjustments, and verify configuration consistency before committing modifications into the live production routing environment, ensuring robust administrative error control and high network stability.

Question 342

Which OSPF Link-State Advertisement type is specifically flooded by an Autonomous System Boundary Router to advertise external network prefixes into the OSPF domain?

1. Type 1 Router LSA
2. Type 2 Network LSA
3. Type 3 Summary LSA
4. Type 5 External LSA

Correct Answer: 4

Explanation

Type 5 External LSAs are generated and flooded across an entire OSPF routing domain by an Autonomous System Boundary Router when redistributing external routes from other routing protocols or static sources. Unlike Type 1 or Type 2 LSAs that remain contained within local areas, Type 5 LSAs traverse area boundaries (passing through ABRs) to provide reachability to external destination prefixes. Routers use these advertisements alongside Type 4 ASBR summary LSAs to calculate paths to external gateways, enabling seamless hybrid network integration across disparate routing domains.

Question 343

What specialized BGP attribute is appended by an internal Route Reflector to track which reflection clusters a route advertisement has traversed, preventing routing loops?

1. Cluster-List attribute
2. Originator-ID attribute
3. Multi-Exit Discriminator
4. Local Preference weight

Correct Answer: 1

Explanation

The Cluster-List attribute is a well-known optional BGP path attribute utilized exclusively within internal BGP Route Reflection architectures. Because IBGP split-horizon rules prevent a route learned from one peer from being propagated to another, Route Reflectors are deployed to pass updates. To prevent routing loops within reflection topologies, the reflector appends the local cluster ID to the Cluster-List attribute of any reflected route. When a router receives an update, it checks the Cluster-List; if its own cluster ID is already present, the update is dropped instantly, ensuring safe loop prevention.

Question 344

How does Juniper Mist Wired Assurance leverage telemetry data to detect switch hardware or connectivity anomalies?

1. By running manual SNMP polling scripts every four hours
2. By exporting raw binary text logs to local backup servers
3. By correlating real-time gRPC streaming switch telemetry through cloud AI analytics
4. By requiring physical console cable attachments for error audits

Correct Answer: 3

Explanation

Juniper Mist Wired Assurance modernizes campus network infrastructure management by replacing legacy polling protocols with real-time gRPC streaming telemetry. EX series switches continuously stream rich operational metrics—including interface error counters, environmental temperatures, PoE power delivery, and LLDP neighbor states—directly into the Mist cloud architecture. The platform’s artificial intelligence engine continuously analyzes these streaming data feeds to isolate root causes, detect anomalies, and deliver proactive notifications and remediation steps before end-user experience is impacted.

Question 345

What is the primary operational characteristic of a Junos forwarding routing instance type?

1. Running independent OSPF and BGP routing protocol daemons
2. Providing isolated Layer 3 forwarding tables without running routing protocol daemons
3. Translating Layer 2 MAC addresses into public IPv6 subnet allocations
4. Encrypting all inter-subnet packet flows with hardware-based IPsec keys

Correct Answer: 2

Explanation

A forwarding routing instance in Junos OS is designed specifically to provide lightweight, isolated Layer 3 forwarding tables without instantiating independent routing protocol daemons. This specialized virtualization model is frequently deployed for technologies like MPLS VPN customer edge routing or specialized traffic path separation, where packet routing lookups must remain segregated while maintaining high-performance hardware forwarding speeds across enterprise platforms without the control-plane overhead of running separate protocol instances.

Question 346

What happens immediately on an enterprise switch port configured with Spanning Tree BPDU Guard when an unauthorized bridge protocol data unit is received?

1. The port transitions into an error-disabled shutdown state instantly
2. The incoming BPDU frame is encrypted and forwarded to the root bridge
3. The port switches automatically to a 10 Mbps half-duplex legacy mode
4. The switch reboots its management routing engine module

Correct Answer: 1

Explanation

Spanning Tree BPDU Guard is a vital layer two security feature designed to protect enterprise network topologies from unauthorized device connections or misconfigurations. User-facing access ports connected to end-user workstations or IP phones should never receive bridge protocol data units. If an administrator or user connects an unauthorized external switch or routing bridge to a port running BPDU Guard, the switch intercepts the incoming BPDU frame and immediately places the interface into an error-disabled state, effectively shutting down the port to prevent loops and topology corruption.

Question 347

In Junos routing policies, which structural components are required to define conditional match rules and execution instructions respectively?

1. match and action
2. filter and target
3. condition and result
4. from and then

Correct Answer: 4

Explanation

Junos routing policies are organized into named term blocks, where each term functions as a logical rule container housing matching criteria and execution instructions. The from clause defines the match conditions that an incoming or outgoing route must satisfy—such as matching specific IP prefixes, route origins, protocol types, or BGP community strings. If a route successfully matches the criteria specified in the from statement, the policy then executes the corresponding instructions defined within the companion then action clause, ensuring precise traffic engineering control.

Question 348

What specific wireless performance metric does the Mist Coverage Service Level Expectation framework monitor and evaluate?

1. Inter-access point roaming handover success rates and latency
2. Real-world signal strength relative to client density parameters across office spaces
3. Total client onboarding authentication and DHCP allocation duration
4. Maximum available downstream throughput link speeds on client devices

Correct Answer: 2

Explanation

The Coverage Service Level Expectation metric within the Juniper Mist platform monitors and evaluates real-world wireless signal strength and coverage quality across enterprise environments. Instead of relying purely on static Received Signal Strength Indicator readings, the Coverage SLE correlates signal levels with client density parameters to ensure that users maintain adequate connection quality throughout office spaces. If signal drops or coverage holes emerge, Mist highlights the anomaly, allowing engineers to optimize access point placement and radio power profiles.

Question 349

What operational timer interval does Link Aggregation Control Protocol utilize when operating in fast transmission (short timeout) mode?

1. Transmission every 30 seconds with 90-second timeouts
2. Transmission every 10 seconds with 30-second timeouts
3. Transmission every 1 second with 3-second timeouts
4. Transmission every 60 seconds with 180-second timeouts

Correct Answer: 3

Explanation

Link Aggregation Control Protocol supports adjustable timer intervals to control how frequently member interfaces exchange LACP Data Units. By default, LACP operates in slow mode, transmitting control frames every 30 seconds. However, configuring fast transmission mode (short timeout) forces member ports to transmit LACPDU heartbeats every 1 second, with a failure dead timeout of 3 seconds. This rapid exchange enables member switches to detect physical link failures, transceiver issues, or member drops almost instantly, greatly improving high-availability convergence times across critical network backbones.

Question 350

Which Junos configuration hierarchy branch is utilized to configure system event logging facilities and remote syslog forwarding destinations?

1. set system syslog
2. set protocols log-server
3. set routing-options forward-log
4. set firewall log-target

Correct Answer: 1

Explanation

In Junos OS, all event logging parameters are configured under the system syslog hierarchy branch. Administrators can define specific log files, facility severities (such as notice, info, warning, or error), and remote syslog server destination IP addresses. This structured configuration ensures that critical security events, operational warnings, and hardware alerts are archived securely off-box to external log management platforms, facilitating comprehensive security auditing and centralized troubleshooting workflows.

Question 351

How is the OSPF Router ID selected on a Junos routing platform if no explicit static Router ID configuration statement is present?

1. By selecting the lowest MAC address on the physical management port
2. By choosing the IP address assigned to the first Ethernet interface in sequence
3. By querying the primary DHCP server during system boot initialization
4. By selecting the highest IP address configured on any active loopback interface

Correct Answer: 4

Explanation

The OSPF Router ID is a 32-bit dotted-decimal identifier required to uniquely identify every router within an OSPF domain. When configuring OSPF on Junos devices, administrators can explicitly define a static Router ID. If this optional statement is omitted, Junos follows a deterministic fallback election process: it automatically selects the highest IP address configured across any active loopback interfaces (lo0). If no loopback interfaces have IP addresses assigned, the system selects the highest IP address configured on any active physical interface, ensuring stable identification.

Question 352

During BGP path selection, what specific condition must be met for a router to evaluate the Multi-Exit Discriminator (MED) attribute between competing routes?

1. The routes must originate from the same neighboring autonomous system
2. The routes must have identical AS-Path lengths and local preference values
3. The routes must be learned via internal BGP peer sessions only
4. The routes must share the exact same OSPF area identifier

Correct Answer: 1

Explanation

The Multi-Exit Discriminator is an optional non-transitive BGP attribute used to advertise the preferred entry point into an autonomous system. However, comparing MED values across routes originating from completely different autonomous systems is mathematically invalid because internal routing metrics differ across providers. Consequently, standard BGP path selection dictates that the MED attribute is only compared between competing external routes received from the same neighboring autonomous system, provided all higher-priority attributes like Local Preference and AS-Path length match.

Question 353

What validation check does Dynamic ARP Inspection perform on untrusted switch ports to protect against ARP spoofing attacks?

1. Encrypting all ARP payload packets with pre-shared cryptographic keys
2. Validating incoming ARP frames against verified IP-to-MAC bindings in the DHCP snooping database
3. Dropping all ARP packets that originate from wireless client access points
4. Limiting the total number of broadcast frames permitted per second

Correct Answer: 2

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 354

Which Junos operational command displays granular interface statistics, including CRC error tallies, framing errors, and output queue drop counts?

1. show interface terse
2. show interface extensive
3. show route summary
4. show bgp summary

Correct Answer: 2

Explanation

The show interface extensive command is a comprehensive diagnostic tool used by network engineers to inspect deep operational metrics on Junos routing and switching platforms. While terse or summary commands provide basic status indicators, the extensive command outputs granular details including physical link layers, duplex states, queue drop counts, CRC error tallies, framing errors, and octet transfer totals. This wealth of diagnostic data is critical when troubleshooting intermittent physical cabling faults, duplex mismatches, or interface congestion bottlenecks across enterprise networks.

Question 355

Which onboarding phase metrics are tracked by the Mist Client Connect Time Service Level Expectation framework?

1. Association, 802.1X authentication handshakes, and DHCP address allocation
2. Inter-access point roaming handover duration and packet loss
3. Signal strength relative to environmental interference and client density
4. Actual client data rates compared to maximum capabilities

Correct Answer: 1

Explanation

The Client Connect Time Service Level Expectation metric within the Juniper Mist platform measures the end-to-end duration required for wireless clients to successfully onboard onto the network. It tracks key phases including association, 802.1X authentication handshakes, and DHCP address allocation. By continuously monitoring connect times and categorizing failures into specific root causes—such as DHCP timeouts or authentication rejections—Mist enables IT administrators to quickly diagnose and resolve onboarding bottlenecks affecting user experience.

Question 356

What is the default routing policy import behavior in Junos OS when no explicit import policy is applied to an active routing protocol?

1. All routing updates learned from active protocol neighbors are accepted by default
2. All incoming routing updates are dropped completely until a policy is defined
3. Only static routes are permitted while dynamic routes are rejected
4. All routes are assigned a default preference value of 255

Correct Answer: 1

Explanation

Junos OS enforces strict default routing policy rules to balance operational usability with control-plane security. By default, the routing engine accepts all valid routing updates learned from active protocol neighbors (import policy permits everything). Conversely, default export behavior rejects all transit routes learned via interior or exterior routing protocols unless an explicit export policy permits them. This asymmetric default design ensures that routers automatically learn external topology information while preventing accidental route leakage back out to external networks.

Question 357

How is the Master routing engine determined when multiple member switches form a Juniper Virtual Chassis stack?

1. By selecting the switch with the lowest serial number on boot
2. By electing the switch with the highest configured routing engine priority value
3. By querying the primary DHCP server across stacking ports
4. By choosing the switch connected to the primary uplink port

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, while the switch with the second-highest priority assumes the Backup role. All remaining member switches function as line card routing units, participating in the distributed forwarding plane while maintaining synchronization with the shared control plane to ensure high availability and automated failover resiliency.

Question 358

Which OSI model layer does MACsec operate on to provide transparent point-to-point data encryption and integrity?

1. Layer 1 Physical layer
2. Layer 2 Data Link layer
3. Layer 3 Network layer
4. Layer 4 Transport 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 359

How does Marvis Actions prioritize network anomalies and failure events for enterprise IT administrators?

1. By sorting alerts strictly by switch model numbers and manufacturing dates
2. By generating random support tickets every calendar hour
3. By analyzing scope, impact, and frequency of issues to highlight high-priority root causes
4. By checking physical copper cable color codes in wiring closets

Correct Answer: 3

Explanation

Marvis Actions uses advanced AI and machine learning telemetry correlation to analyze network health. Instead of treating all alerts equally, Marvis evaluates the scope (number of affected users), impact (severity of failure), and frequency of anomalies, intelligently prioritizing critical root causes so IT teams can resolve high-impact issues first. This automated triage capability drastically reduces mean-time-to-resolution and eliminates alert fatigue for enterprise support personnel.

Question 360

What is the functional purpose of the candidate configuration database in Junos OS?

1. Storing permanent firmware binary installation images
2. Caching web server files for faster guest network browsing
3. Holding uncommitted staging modifications safely before they are applied to production
4. Maintaining historical rollback snapshots for system recovery

Correct Answer: 3

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 using validation commands, executing a commit command applies the candidate changes to the active running database, ensuring robust operational stability and safe administrative control.