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

 

Question 121

Which operational command creates a permanent rescue configuration backup in Junos OS?

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 122

What primary purpose do Juniper Mist Client Service Level Expectations serve in enterprise wireless networks?

1. Encrypting client payload packets
2. Tracking real-time wireless user experience
3. Limiting PoE wattage draw on switches
4. Allocating static IP addresses to APs

Correct Answer: 2

Explanation

Service Level Expectations serve as the essential foundation for measuring actual user experience within the modern Mist architecture. Instead of relying solely on infrastructure uptime metrics, SLEs track client-centric parameters like connection time, throughput, roaming performance, and coverage. Each metric is evaluated continuously against predefined thresholds, enabling administrators to isolate whether connection failures stem from DHCP starvation, DNS latency, authentication timeouts, or physical signal degradation. This shifts the operational focus from device monitoring to true end-user experience tracking.

Question 123

Which parameter takes precedence first when an OSPF router determines its Router ID automatically?

1. Highest active IP address on any interface
2. Highest IP address configured on a loopback interface
3. Lowest MAC address assigned to the routing engine
4. First statically defined administrative string

Correct Answer: 2

Explanation

When an OSPF routing process initializes without a manually configured Router ID, it selects one automatically based on specific operational criteria. First, the router checks all active loopback interface IP addresses and picks the highest numeric IP address. If no loopback interfaces are configured and operational, the router compares all active physical interface IP addresses and selects the highest numeric value among them. Setting a static loopback IP address is considered a best practice to ensure stable, predictable OSPF routing adjacencies.

Question 124

What happens when a non-master member switch is removed from an active Juniper Virtual Chassis?

1. The entire stack reboots instantly
2. Remaining members continue forwarding traffic normally
3. All network interfaces shut down automatically
4. Routing protocol databases are erased

Correct Answer: 2

Explanation

Juniper Virtual Chassis technology provides robust high availability and resilience across stacked EX Series switches. If a non-master member switch is powered down or physically removed from the stack, the remaining member switches detect the topology change and continue forwarding traffic without interruption, assuming redundant uplinks and ring paths are configured correctly. The distributed control plane and link aggregation groups ensure that peripheral device connectivity remains stable while the stack adapts dynamically to the modified physical topology.

Question 125

What is the primary security objective of Dynamic ARP Inspection on access switch ports?

1. Blocking rogue DHCP server replies
2. Preventing man-in-the-middle ARP spoofing
3. Encrypting layer two user data frames
4. Authenticating 802.1X client credentials

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 to protect network segments.

Question 126

Which BGP path selection attribute is evaluated first during standard route comparison?

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

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 127

Which operational command displays the historical commit log and configuration changes in Junos OS?

1. show system commit
2. show configuration history
3. show candidate changes
4. show rescue status

Correct Answer: 1

Explanation

The show system commit command provides a detailed audit trail of historical configuration commits executed on a Junos device. When invoked, it displays commit timestamps, user account names associated with the changes, client transport methods used, and optional commit comment tags. This command is invaluable for network engineers tracking administrative changes, investigating unexpected network faults, and reviewing configuration lifecycles across enterprise routing and switching platforms.

Question 128

What specific security function does MACsec encryption provide across enterprise switch links?

1. Layer 2 confidentiality and integrity
2. Layer 3 IPsec tunnel establishment
3. Layer 4 transport port filtering
4. Layer 7 application payload scanning

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 129

What is the core function of Mist Edge in distributed campus and remote branch architectures?

1. Local web server proxy caching
2. Tunnel aggregation and traffic steering
3. Dynamic OSPF route calculation
4. Core database hardware replication

Correct Answer: 2

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 130

Which Rapid Spanning Tree Protocol port role immediately replaces the root port if the active root link fails?

1. Designated port role
2. Alternate port role
3. Backup port role
4. Disabled port role

Correct Answer: 2

Explanation

Under Rapid Spanning Tree Protocol, the alternate port role represents a port that receives superior BPDU information from another switch but is blocked because it is not the chosen path to the root bridge. If the primary root port on a switch experiences a physical link failure, the alternate port transitions immediately into the root port forwarding state without enduring legacy listening and learning delays. This rapid transition mechanism ensures minimal application downtime during topology reconvergence.

Question 131

Which Junos operational command displays comprehensive physical interface error counters and CRC drops?

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

Correct Answer: 1

Explanation

The show interface extensive command provides a comprehensive, itemized diagnostic output for physical and logical interfaces configured on a Junos routing or switching platform. It displays comprehensive operational statistics including packet counts, byte rates, error counters, CRC drops, queue drops, physical duplex settings, encapsulation types, and specific hardware transceiver diagnostics. This command is an indispensable asset for network engineers troubleshooting physical layer issues, bad patch cables, or interface congestion.

Question 132

What is a defining characteristic of an OSPF stub area configuration?

1. External AS-routes are flooded everywhere
2. External AS-routes are blocked and replaced by a default route
3. Internal router adjacencies are disabled completely
4. Hello timer intervals must exceed sixty seconds

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 133

What operational benefit does creating a virtual router instance provide on Juniper platforms?

1. Layer 2 bridge domain flooding
2. Complete IP routing table separation
3. Automated wireless channel tuning
4. Hardware transceiver power amplification

Correct Answer: 2

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.

Question 134

How does the Marvis Actions framework assist engineers during network troubleshooting sessions?

1. By running automated cable tester sweeps
2. Through a conversational natural language interface
3. By rebooting malfunctioning switch hardware
4. Through manual CLI script generation

Correct Answer: 2

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 135

What action does a switch port configured with port-security violation shutdown take upon receiving an unauthorized MAC address?

1. Drops traffic and logs syslog message
2. Disables the physical interface completely
3. Forwards packets without any restrictions
4. Translates the source address dynamically

Correct Answer: 2

Explanation

When port security is configured with the shutdown violation mode, the switch immediately disables the physical interface and turns off the link when an unauthorized MAC address exceeds configured limits or appears on an untrusted port. This aggressive security response isolates potential network intrusions or rogue endpoint attachments instantly. The port remains in an error-disabled state until an administrator manually intervenes to troubleshoot the issue and re-enable the interface via the command-line interface.

Question 136

What operational state combination allows LACP to establish an active link aggregation bundle successfully?

1. Active mode on both peer devices
2. Passive mode configured on both peers
3. Active mode on one peer and passive on the other
4. Static pinning without control packets

Correct Answer: 3

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, and aggregation fails.

Question 137

What character typically signifies that a Junos device is currently operating in operational monitoring mode?

1. The greater-than sign (>)
2. The hash pound symbol (#)
3. The percent sign (%)
4. The dollar sign ($)

Correct Answer: 1

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 that the user has read-only access to monitoring commands, statistics, ping diagnostics, and system 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 are enabled.

Question 138

How does a switch identify trusted ports versus untrusted ports when DHCP Snooping is enabled?

1. By inspecting physical cable color codes
2. Through manual administrative configuration commands
3. By analyzing incoming MAC address prefixes
4. Based on Spanning Tree root bridge priorities

Correct Answer: 2

Explanation

When configuring DHCP Snooping on enterprise access switches, network administrators must explicitly define which switch ports connect to legitimate, authorized corporate DHCP servers as trusted ports. All other user-facing access ports default to untrusted status. This administrative designation is critical because the switch relies on it to intercept and drop bogus offer messages originating from unauthorized rogue DHCP servers connected to untrusted ports, protecting enterprise clients from IP starvation attacks.

Question 139

What specific security protection does Spanning Tree BPDU Guard provide on edge switch ports?

1. Blocking unauthorized root bridge takeover attempts
2. Disabling ports that receive unexpected bridge protocol data units
3. Encrypting spanning tree control frames
4. Preventing broadcast storm amplification

Correct Answer: 2

Explanation

Spanning Tree BPDU Guard is a protective feature configured primarily on access ports where end-user devices connect. Because user workstations and IP phones should never originate bridge protocol data units, BPDU Guard monitors the port; if a switch or rogue device transmits a BPDU onto an edge port enabled with BPDU Guard, the switch immediately transitions the interface into an error-disabled state. This prevents unauthorized network loops and topology manipulation caused by rogue switches attached to user ports.

Question 140

What primary operational benefit do gRPC streaming telemetry protocols provide over traditional SNMP polling?

1. Lower CPU overhead and real-time data streaming
2. Complete encryption of all physical copper cables
3. Automated conversion of Layer 2 frames to Layer 7 apps
4. Elimination of routing protocol neighbor timers

Correct Answer: 1

Explanation

Streaming telemetry powered by gRPC and protocol buffers offers massive operational advantages over legacy SNMP polling methods. Traditional SNMP requires periodic polling intervals that consume switch CPU cycles and introduce data latency. In contrast, gRPC streaming pushes real-time interface statistics, hardware sensor metrics, and operational counters directly to management platforms on a change-of-state basis. This enables instantaneous visibility and precise analytics without straining switch control plane resources.