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

 

Question 381

Which Junos firewall filter action modifier allows an administrator to track and tally matching packet statistics without altering packet forwarding behavior?

1. count
2. discard
3. reject
4. policer

Correct Answer: 1

Explanation

In Junos OS, the count action modifier can be attached to any firewall filter term to record how many packets and bytes match the specified criteria. When a packet matches the term, the associated counter increments instantly while the packet continues processing through the filter terms normally (passing to the next term or hitting the default policy action). This is an invaluable diagnostic and auditing tool for tracking specific traffic flows, verifying security rule hits, or measuring application bandwidth consumption without disrupting live data plane routing.

Question 382

What is the core operational behavior of an internal BGP (IBGP) Route Reflector client when reflecting route updates?

• Clients must maintain full-mesh peer connections with every other router in the autonomous system
• Clients send routes learned from non-client peers directly to other clients without reflection
• Clients forward routes learned from external peers to the route reflector, which then reflects them to other clients and non-client peers
• Clients bypass all BGP path selection attribute comparisons completely

Correct Answer: 3

Explanation

In an internal BGP Route Reflection architecture, the route reflector eliminates the requirement for a full-mesh IBGP topology by centralizing route propagation. When a Route Reflector receives route updates from a client, a non-client, or an external peer, it reflects those updates across its client group and non-client peers. Client routers themselves do not need full-mesh connections to each other; they simply peer with the route reflector, dramatically scaling large enterprise and service provider networks while preventing routing loops through built-in attributes like Originator-ID and Cluster-List.

Question 383

Which OSPF area type permits the injection of external routes via Type 5 LSAs while blocking summary Type 3 and Type 4 LSAs?

1. Standard Area
2. Totally Stubby Area
3. Not-So-Stubby Area (NSSA) Stub
4. Standard Stub Area

Correct Answer: 3

Explanation

A Not-So-Stubby Area (NSSA) is a specialized OSPF area variant designed to support external route redistribution at the edge of an autonomous system without requiring the area to ingest full external Type 5 LSAs from the rest of the domain. While standard stub areas block external routes entirely, an NSSA allows an internal ASBR to inject external routes using specialized Type 7 LSAs. The area’s ABR then translates these Type 7 LSAs into Type 5 LSAs before flooding them into the backbone area (Area 0), balancing routing reachability with reduced link-state database overhead.

Question 384

How does Juniper Mist Wired Assurance automate the detection of switch port misconfigurations or cabling faults?

1. By running manual ping scripts every Sunday midnight
2. By exporting raw binary text logs to local TFTP repositories
3. By analyzing real-time gRPC streaming switch telemetry and client event correlations through cloud AI
4. By requiring physical console cable attachments for weekly verification audits

Correct Answer: 3

Explanation

Juniper Mist Wired Assurance modernizes campus network management by replacing legacy polling mechanisms with real-time gRPC streaming telemetry. EX series switches continuously stream rich operational metrics—including interface error counters, duplex mismatches, 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 385

Which Junos configuration hierarchy branch is utilized to establish static routing entries and next-hop gateway definitions?

1. set protocols static
2. set routing-options static
3. set system routing-table
4. set interfaces static-route

Correct Answer: 2

Explanation

In Junos OS, all static routing configurations are managed under the routing-options static hierarchy branch. Administrators use this branch to define static destination IP prefixes and assign corresponding next-hop gateway IP addresses, discard actions, or recursive lookup parameters. The structured hierarchical design ensures that static routes are clearly organized and separated from dynamic routing protocols like OSPF and BGP, providing reliable fallback routing capabilities across enterprise network platforms.

Question 386

What operational benefit does enabling Rapid Spanning Tree Protocol (RSTP) edge ports provide on switch interfaces connected to end-user workstations?

1. Bypassing the listening and learning states to transition the port immediately to forwarding upon link up
2. Encrypting all outgoing data frames with AES-256 cryptographic keys
3. Converting physical Ethernet ports into wireless radio access points automatically
4. Translating private IP addresses into public internet spaces instantly

Correct Answer: 1

Explanation

In legacy Spanning Tree Protocol, switch ports connecting to end-user devices still had to pass through the listening and learning states, resulting in a 30-to-50-second delay before client devices could communicate. RSTP introduces the concept of edge ports (similar to PortFast), which allows ports connected directly to end-stations (like PCs or IP phones) to transition immediately from blocking to forwarding state as soon as the physical link comes up, eliminating unnecessary startup delays while maintaining loop protection.

Question 387

Which category of BGP path attributes is defined as mandatory for all routers to recognize and support, and must be included in every valid route advertisement?

1. Well-known discretionary attributes
2. Well-known mandatory attributes
3. Optional transitive attributes
4. Optional non-transitive attributes

Correct Answer: 2

Explanation

BGP path attributes are strictly categorized to ensure interoperability across diverse vendor implementations. Well-known mandatory attributes—such as Origin, AS-Path, and Next-Hop—must be recognized by all standard-compliant BGP routers and must be present in every update message describing a valid route. If a router receives an update missing a well-known mandatory attribute, it generates a notification error and resets the BGP peering session, maintaining strict protocol integrity.

Question 388

Which Junos operational command displays the active Layer 2 MAC address forwarding table entries learned by a switch?

1. show route
2. show bridge mac-table
3. show bgp summary
4. show system alarms

Correct Answer: 2

Explanation

The show bridge mac-table command (or show ethernet-switching table depending on the platform generation) is an essential operational tool used by network engineers to inspect Layer 2 forwarding states on Juniper switching platforms. When executed, it outputs learned source MAC addresses, associated VLAN identifiers, incoming interface ports, and aging timers. This data is critical when troubleshooting connectivity issues, tracking client locations, or verifying VLAN trunking configurations across campus networks.

Question 389

What performance vector does the Mist Client Connect Time Service Level Expectation framework track to measure onboarding health?

1. Total time required for client association, 802.1X authentication, and DHCP IP address allocation
2. Inter-access point roaming handover latency and packet drop rates
3. Signal strength relative to client density and environmental interference
4. Actual client throughput speeds compared to maximum link 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 390

Within a Juniper Virtual Chassis configuration, what operational role is assumed by the member switch possessing the highest configured routing engine priority value?

1. Backup routing engine
2. Primary Master role
3. Standalone passive line card
4. Core firewall gateway

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 control-plane operations, routing protocol execution, and management synchronization. The switch with the second-highest priority assumes the Backup role, while all remaining members function as line card forwarding units, ensuring high availability and automated failover resiliency.

Question 391

What tie-breaking parameter is evaluated immediately after Router Priority when determining the OSPF Designated Router on a multi-access network segment?

1. Highest OSPF Router ID
2. Lowest physical MAC address
3. Highest loopback interface IP address
4. Lowest management port port number

Correct Answer: 1

Explanation

When OSPF routers establish adjacencies on a multi-access broadcast network segment (such as an Ethernet LAN), they hold an election to select a Designated Router and Backup Designated Router to minimize routing protocol traffic. The election process first evaluates the configurable OSPF Router Priority value (ranging from 0 to 255, where 0 removes the router from contention). If router priorities are tied, OSPF evaluates the 32-bit Router ID, selecting the router with the highest numerical Router ID as the Designated Router.

Question 392

Which Junos command allows an administrator to instantly revert the active configuration back to the designated rescue baseline file?

1. rollback rescue
2. request system factory-default
3. clear configuration candidate
4. commit check

Correct Answer: 1

Explanation

The rollback rescue command (executed from configuration mode) is a vital emergency recovery mechanism in Junos OS. If an experimental configuration change causes severe network disruption or locks out management access, an administrator can enter the rescue rollback command to instantly load the pre-saved, verified rescue baseline into the candidate buffer, followed by a commit. This restores normal network operations immediately without requiring physical console intervention or device reboots.

Question 393

Which IEEE standard defines MACsec point-to-point Layer 2 data encryption, integrity, and origin authenticity?

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

Correct Answer: 2

Explanation

MACsec is standardized under IEEE 802.1AE and provides robust point-to-point data encryption, data integrity, and origin authenticity directly at Layer 2 of the OSI model. By securing Ethernet links between switches or client endpoints, MACsec protects enterprise networks against wiretapping, MAC address spoofing, and passive eavesdropping attacks without altering higher-layer network protocols or routing configurations, making it an essential security standard for sensitive campus backbones.

Question 394

During BGP path selection, which comparison attribute is evaluated immediately after checking the local preference value?

1. Origin code type (IGP, EGP, Incomplete)
2. Shortest AS-Path length
3. Lowest Multi-Exit Discriminator value
4. Oldest router ID identifier

Correct Answer: 2

Explanation

Border Gateway Protocol follows a strict, sequential decision process to select the optimal path to any destination prefix. After evaluating the highest Local Preference value (which is checked first), BGP proceeds to examine the AS-Path length attribute. Paths with the shortest AS-Path length are preferred, as they traverse fewer autonomous systems to reach the destination. If AS-Path lengths are equal, the decision process continues down the chain to evaluate origin codes, MED values, and neighbor types.

Question 395

What is the functional characteristic of a Junos vrf (Virtual Routing and Forwarding) routing instance type?

1. Providing standalone Layer 2 bridging isolation without IP routing
2. Maintaining an isolated Layer 3 routing table, interface bindings, and routing protocols for VPN deployments
3. Translating private IPv4 addresses into public internet spaces automatically
4. Encrypting all inter-subnet packet flows with hardware-based IPsec keys

Correct Answer: 2

Explanation

A vrf routing instance in Junos OS creates a fully isolated Layer 3 routing and forwarding environment, widely used in MPLS VPNs and multi-tenant enterprise architectures. A VRF instance maintains its own independent routing table, distinct interface assignments, and isolated routing protocol daemons (such as OSPF or BGP). This allows multiple customers or organizational departments to utilize overlapping IP address spaces across the same physical hardware infrastructure while maintaining absolute logical separation.

Question 396

What operational distinction separates trusted ports from untrusted ports when configuring DHCP Snooping on enterprise switches?

1. Trusted ports drop all incoming DORA packet streams instantly
2. Untrusted ports are restricted from originating DHCP server reply messages, preventing rogue server spoofing
3. Trusted ports require manual cryptographic key authentication for every frame
4. Untrusted ports operate exclusively at legacy 10 Mbps half-duplex settings

Correct Answer: 2

Explanation

DHCP Snooping classifies switch ports as either trusted or untrusted to protect enterprise networks from malicious rogue DHCP servers. Trusted ports connect to authorized upstream DHCP servers or core switches and are permitted to transmit all DHCP messages (including DHCPOFFER and DHCPACK). Untrusted ports connect to end-user access devices; any DHCP server reply messages arriving on an untrusted port are blocked and dropped instantly by the switch, preventing attackers from assigning malicious gateway IPs to unsuspecting clients.

Question 397

How do Junos configuration groups (groups) inherit and apply parameters across hierarchical configuration branches?

1. By replacing the entire running configuration with a single static text file
2. By matching wildcard criteria and applying defined parameter blocks dynamically where invoked via apply-groups
3. By encrypting all configuration files automatically every midnight
4. By converting CLI commands into legacy vendor syntax structures

Correct Answer: 2

Explanation

Junos configuration groups provide a powerful template-driven inheritance mechanism that allows network administrators to define modular, reusable blocks of configuration parameters once and apply them dynamically across multiple interfaces, routing protocols, or system hierarchies. Using wildcard variables and match statements, configuration groups are activated using the apply-groups statement, drastically reducing human error and repetitive CLI typing across large-scale enterprise deployments.

Question 398

How does the Marvis Virtual Network Assistant enhance troubleshooting workflows within the Juniper Mist platform?

1. By translating natural language English queries into automated telemetry diagnostics and actionable root-cause remediation
2. By running manual ping scripts every calendar hour without user input
3. By converting all operational syslog entries into physical paper printouts
4. By forcing switches and access points into factory default states upon error detection

Correct Answer: 1

Explanation

The Mist Virtual Network Assistant features a powerful conversational interface powered by Marvis AI. Instead of navigating complex multi-layered dashboards or manually parsing through raw telemetry logs, administrators can type or speak queries in plain English (such as “Why did user device X fail authentication today?”). Marvis instantly interprets the underlying telemetry data, correlates client events across wireless and wired domains, and delivers precise diagnostic breakdowns along with actionable remediation steps to resolve issues rapidly.

Question 399

What is the operational effect of configuring Link Aggregation Control Protocol (LACP) in active mode on a switch interface?

1. The interface actively transmits LACP protocol frames to initiate and negotiate an aggregated bundle with its peer
2. The interface disables all Layer 2 forwarding until a manual serial console cable is attached
3. The interface converts into a dedicated OSPF routing point automatically
4. The interface drops all incoming Spanning Tree bridge protocol data units

Correct Answer: 1

Explanation

Link Aggregation Control Protocol defines specific operational modes for member interfaces to govern how protocol control packets are exchanged. An interface configured in active mode actively initiates LACP negotiation by transmitting LACPDU protocol frames toward the neighboring switch, whereas a passive mode interface responds to incoming LACP frames but does not initiate them. For an LACP bundle to form successfully across peer devices, at least one participating peer must be configured in active mode.

Question 400

What core architectural advantage does the integration of Juniper Mist AI and Wired/Wireless Assurance provide to enterprise IT operations?

1. Complete elimination of all physical routing and switching hardware components
2. Transitioning from reactive, device-centric monitoring to proactive, user-centric AI-driven automation and root-cause isolation
3. Mandating manual configuration of every switch port via legacy command-line interfaces
4. Replacing all dynamic routing protocols with static default routes

Correct Answer: 2

Explanation

The integration of Juniper Mist AI and Wired/Wireless Assurance redefines enterprise networking by shifting focus from traditional device-centric metrics (like CPU and memory usage) to direct user-centric experience metrics using the Service Level Expectation framework. By leveraging real-time gRPC streaming telemetry, machine learning correlation, and the Marvis conversational assistant, Mist transforms reactive troubleshooting into proactive automated resolution, drastically reducing mean-time-to-resolution and simplifying campus network management.