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

 

Question 221

Which Junos operational command is used to check available disk space, partition usage, and flash memory utilization?

1. show system storage
2. show chassis hardware
3. show system resources
4. show version detail

Correct Answer: 1

Explanation

The show system storage command provides a detailed breakdown of file system disk space utilization across internal flash drives, hard disks, and logging partitions on a Junos device. Network administrators use this command to monitor partition health, ensure adequate space exists for software upgrades or log archives, and prevent system instability caused by full storage volumes.

Question 222

What is the default preference value assigned to static routes in Junos OS?

1. 1
2. 5
3. 60
4. 170

Correct Answer: 2

Explanation

In Junos OS, route preference (analogous to Administrative Distance in other networking vendor operating systems) dictates the trustworthiness of routing information sources. The default preference value for direct routes is 0, local routes is 0, and static routes is 5. OSPF carries a default preference of 10, while external BGP has a default preference of 170. Lower numerical preference values are always preferred when the routing engine selects active paths.

Question 223

What is the primary operational purpose of an OSPF Virtual Link?

1. Encrypting traffic between two physical areas over public IP networks
2. Connecting a disconnected non-backbone area back to Area 0 through a transit area
3. Replacing traditional Area Border Routers with software-defined tunnels
4. Translating Type 7 LSAs into standard Type 5 external routes

Correct Answer: 2

Explanation

An OSPF Virtual Link is a specialized architectural tool used when a non-backbone area cannot physically connect directly to the central backbone area (Area 0). By establishing a virtual link across an intervening transit area, OSPF allows the isolated area to maintain logical adjacency and routing exchange with the backbone, ensuring proper topology convergence without requiring physical recabling.

Question 224

How does the IBGP split-horizon rule prevent routing loops within an Autonomous System?

1. By dropping updates received from external peers directly
2. By preventing a route learned from one IBGP peer from being advertised to another IBGP peer
3. By modifying the MED attribute on local egress boundaries
4. By incrementing the AS-Path length count on every internal hop

Correct Answer: 2

Explanation

Unlike EBGP, where the AS-Path attribute prevents loops across different autonomous systems, IBGP does not alter the AS-Path when advertising routes internally. To prevent routing loops within the same AS, the IBGP split-horizon rule mandates that routes learned from one IBGP peer cannot be advertised to another IBGP peer. This rule requires full-mesh IBGP peerings or the deployment of route reflectors and confederations.

Question 225

What IEEE standard defines Multiple Spanning Tree Protocol (MSTP), allowing multiple VLANs to be mapped into common spanning tree instances?

1. IEEE 802.1D
2. IEEE 802.1w
3. IEEE 802.1s
4. IEEE 802.1ad

Correct Answer: 3

Explanation

Multiple Spanning Tree Protocol is standardized under IEEE 802.1s (later integrated into IEEE 802.1Q). MSTP improves upon legacy STP and RSTP by enabling administrators to group multiple VLANs into shared spanning tree instances. This reduces the total number of active spanning tree protocol instances running across the network, conserves CPU and memory resources, and allows efficient load balancing of traffic across redundant trunk links.

Question 226

What is the default routing policy export behavior in Junos OS when no explicit export policy is applied?

1. All direct and local routes are exported, while transit routes learned from protocols are rejected
2. All active routes in the routing table are exported to every neighbor automatically
3. All routing updates are dropped completely until a policy is defined
4. Only static routes are advertised to external peers

Correct Answer: 1

Explanation

Junos OS enforces strict default routing policy rules. By default, the routing engine exports direct routes and local interface routes to downstream peers, but it rejects all transit routes learned via interior or exterior routing protocols unless an explicit export policy permits them. Conversely, the default import policy accepts all valid routing updates learned from active protocol neighbors.

Question 227

What specific security function does Traffic Storm Control provide on enterprise switch ports?

1. Encrypting broadcast frame payloads using pre-shared keys
2. Monitoring and dropping excessive broadcast, multicast, or unknown unicast traffic
3. Authenticating wireless client credentials via 802.1X
4. Blocking unauthorized root bridge takeover attempts

Correct Answer: 2

Explanation

Traffic Storm Control is a vital layer two security and performance feature that monitors incoming traffic levels on switch ports. If broadcast, multicast, or unknown unicast traffic frames exceed a predefined percentage threshold of total link bandwidth, the switch drops the excess frames to prevent network congestion, high CPU utilization, and system stalls.

Question 228

What command is used on a dual Routing Engine Junos device to synchronize candidate configurations across both engines?

1. commit synchronize
2. commit check
3. commit confirmed
4. commit rescue

Correct Answer: 1

Explanation

The commit synchronize command ensures high availability across redundant dual Routing Engine platforms. When executed, it validates and applies the candidate configuration to the primary active Routing Engine while simultaneously pushing and applying the identical configuration to the backup Routing Engine. This guarantees that both control planes remain completely synchronized in the event of a failover.

Question 229

What is the core function of the Mist Client Capacity Service Level Expectation metric?

1. Evaluating roaming handoff duration between APs
2. Tracking whether access points have sufficient client capacity and airtime availability
3. Measuring cable transceiver signal attenuation levels
4. Monitoring Power over Ethernet wattage distribution on switches

Correct Answer: 2

Explanation

The Client Capacity Service Level Expectation metric within the Juniper Mist platform evaluates whether wireless access points are experiencing congestion or lacking sufficient airtime and client capacity. It monitors metrics such as client counts, signal data rates, and channel utilization to ensure that devices are not bottlenecked by overloaded radios or poor architectural placement.

Question 230

Which BGP path attribute is classified as a well-known mandatory attribute?

1. Local Preference
2. AS-Path
3. Multi-Exit Discriminator
4. Community

Correct Answer: 2

Explanation

Border Gateway Protocol attributes are categorized into four classes: well-known mandatory, well-known discretionary, optional transitive, and optional non-transitive. The AS-Path attribute, along with ORIGIN and NEXT_HOP, is classified as a well-known mandatory attribute. This means every BGP routing update must recognize and support these attributes, and they are propagated across all autonomous systems.

Question 231

What wireless standard is commonly known as Fast Roaming, facilitating rapid and secure handoffs between access points?

1. IEEE 802.11ac
2. IEEE 802.11r
3. IEEE 802.11ax
4. IEEE 802.11i

Correct Answer: 2

Explanation

IEEE 802.11r, also known as Fast BSS Transition or Fast Roaming, is a wireless standard designed to streamline authentication key handoffs when a client device moves between different access points within the same enterprise mobility domain. By allowing key negotiation to occur prior to roaming completion, 802.11r drastically reduces roaming latency, preventing packet loss and voice call drops.

Question 232

What type of cables are typically used to interconnect member switches in a Juniper Virtual Chassis configuration?

1. Dedicated Virtual Chassis copper or fiber cable assemblies with specialized transceivers
2. Standard crossover Ethernet patch cables attached to management ports
3. Coaxial RF antenna distribution lines
4. USB serial console rollover cables

Correct Answer: 1

Explanation

Juniper Virtual Chassis configurations rely on dedicated Virtual Chassis Ports (VCPs) and specialized high-speed interconnect cables (such as pre-terminated SFP+ or QSFP+ DAC cables, or dedicated stacking cables depending on the EX switch model). These high-bandwidth links combine control and data planes across member switches to form a unified logical entity.

Question 233

What is the primary purpose of the Marvis Client SDK integrated into mobile and endpoint applications?

1. Providing local battery charging optimization
2. Gathering end-user client telemetry and experience data directly from devices
3. Translating Layer 2 MAC addresses into static IP bindings
4. Automating firmware rollouts on Juniper core switches

Correct Answer: 2

Explanation

The Marvis Client SDK is a software development tool integrated into client devices and applications to gather deep client-side telemetry—such as connection latency, roaming performance, and application responsiveness. By streaming this direct device perspective to the Mist cloud, Marvis achieves unprecedented visibility into end-user experience, bypassing limitations of traditional infrastructure-only monitoring.

Question 234

What specific operational benefit does Junos stateless firewall filtering provide compared to stateful inspection?

1. Complete packet payload encryption across all copper links
2. High-speed packet classification and filtering without maintaining connection state tables
3. Automated dynamic NAT port translation
4. Real-time protocol translation between IPv4 and IPv6

Correct Answer: 2

Explanation

Stateless firewall filters in Junos examine packets independently based on predefined match criteria (such as source/destination IP, ports, or protocols) without tracking connection states or session tables. Because they do not require memory allocation for connection states, stateless filters execute at wire speed on ASIC hardware, making them ideal for high-throughput edge filtering and traffic policing.

Question 235

What is the function of Voice VLAN configuration on Juniper enterprise access switches?

1. Encrypting voice data packets using MACsec
2. Automatically separating and prioritizing IP telephony traffic from standard data traffic
3. Converting analog telephone signals into digital Ethernet frames
4. Providing static power over ethernet boosting to desk phones

Correct Answer: 2

Explanation

Voice VLAN technology allows network administrators to configure switch ports to automatically segregate IP telephone traffic onto a dedicated VLAN, separate from user PC data traffic. This ensures proper Quality of Service (QoS) prioritization, enhances voice call clarity, and simplifies multi-device onboarding on shared physical access ports.

Question 236

Which command displays active hardware revision levels, serial numbers, and module descriptions on a Junos device?

1. show chassis hardware
2. show system software
3. show route summary
4. show interface diagnostics

Correct Answer: 1

Explanation

The show chassis hardware command provides an itemized physical inventory report of all hardware components installed within a Junos routing or switching platform, including serial numbers, part numbers, model descriptions, and manufacturing revision levels for power supplies, fan trays, and interface modules.

Question 237

What operational advantage does dynamic packet capture provide within the Juniper Mist cloud architecture?

1. Capturing and storing packets automatically upon fault detection for remote troubleshooting
2. Encrypting wireless management frames to prevent eavesdropping
3. Translating routing table entries into protocol buffer streams
4. Automatically routing packet captures to local USB flash drives

Correct Answer: 1

Explanation

Mist dynamic packet capture automatically triggers packet captures on access points or switches the moment an anomaly or client connectivity failure occurs. This eliminates the need for engineers to manually recreate intermittent issues or capture traffic on-site, providing instant diagnostic data for faster root cause analysis.

Question 238

Which OSPF router type generates Type 3 Summary LSAs when routing between areas?

1. Internal Router
2. Area Border Router (ABR)
3. Autonomous System Border Router (ASBR)
4. Designated Router (DR)

Correct Answer: 2

Explanation

An OSPF Area Border Router connects one or more areas to the backbone area (Area 0). When routes need to be propagated between areas, the ABR translates interior routing data into Type 3 Summary LSAs, summarizing network prefixes across area boundaries to optimize routing table sizes and protocol convergence.

Question 239

What happens when a Junos commit operation encounters a syntax or semantic error in the candidate configuration?

1. The device applies the invalid configuration partially
2. The commit fails, error messages are displayed, and the running configuration remains untouched
3. The routing engine automatically reboots into recovery mode
4. The candidate configuration is wiped out completely

Correct Answer: 2

Explanation

Junos OS protects production network stability by validating candidate configurations before applying them. If any syntax error, missing dependency, or logical conflict exists, the commit operation is rejected entirely, detailed error logs are presented to the administrator, and the active running configuration continues operating without disruption.

Question 240

Which Mist AI feature allows administrators to search and query network telemetry using plain, conversational English?

1. Marvis Actions
2. Virtual Network Assistant Conversational Interface
3. Wired Assurance Template Engine
4. Mist Edge Tunnel Manager

Correct Answer: 2

Explanation

The Mist Virtual Network Assistant features a powerful natural language conversational interface powered by Marvis AI. Administrators can type or speak queries in plain English (e.g., “Why did device X fail to connect to Wi-Fi?”), and Marvis instantly interprets the telemetry data to deliver precise diagnostic breakdowns and remediation steps.