Nokia 4A0-D01 Nokia Data Center Fabric Fundamentals Exam Exam Practice Test

Comprehensive and Detailed Explanation From Exact Extract:

Option A: FALSE – Checkpoint 0 is the latest (most recent), not the oldest.

"Checkpoints are numbered sequentially, with 0 representing the most recent checkpoint. Higher numbers indicate older checkpoints."

— SR Linux Configuration Management Guide, "Checkpoint Numbering"

Option B: TRUE – Checkpoints are stored as JSON files.

"Checkpoints capture the running configuration in JSON format for easy parsing and restoration."

— SR Linux CLI User Guide, "Checkpoint Operations"

Option C: TRUE – Reversion to any checkpoint is supported.

"Operators can revert to any saved checkpoint, restoring the system to that specific state."

— SR Linux Configuration Management Guide, "Checkpoint Revert"

Option D: TRUE – Checkpoints can be auto-generated on commit.

"The system can be configured to create a new checkpoint automatically upon successful commit."

— SR Linux CLI User Guide, "Commit Options"

Conclusion: Option A is false because checkpoint 0 is the newest.

Comprehensive and Detailed Explanation with Exact Extracts:

Option A is FALSE: Next-hop groups support indirect next-hops (non-local IPs requiring recursive lookup).

Extract from Nokia SR Linux Configuration Guide (Section: Next-Hop Groups):

"The next-hop can be a directly attached IP address or an indirect next-hop (e.g., a router IP not on a directly connected subnet)."

Option B is TRUE: Next-hop groups are reusable objects referenced by multiple static routes.

Extract from Nokia SR Linux Configuration Guide (Section: Next-Hop Groups):

"A single next-hop group can be referenced by multiple static routes, simplifying configuration for shared forwarding behavior."

Option C is FALSE: Blackhole next-hop groups silently drop traffic by default. ICMP unreachable messages require explicit configuration.

Extract from Nokia SR Linux Configuration Guide (Section: Blackhole Routes):

"When blackhole is configured, traffic is discarded without sending ICMP unreachable messages unless send-blackhole-icmp true is explicitly set."

Option D is FALSE: Next-hop groups support ECMP with multiple next-hops.

Extract from Nokia SR Linux Fundamentals Guide (Section: Next-Hop Groups):

"A next-hop group can define multiple next-hops for Equal-Cost Multi-Path (ECMP) load balancing."

Comprehensive and Detailed Explanation:

Nokia’s Fabric Services System (FSS) employs an intent-driven approach where the fabric intent is defined in a YAML file. This file specifies the desired state of the data center fabric, including topology, services, and policies. FSS translates this declarative intent into device-specific configurations.

Exact Extract:

"Fabric Services System uses intent-based YAML templates to define the fabric’s target state. The system automates configuration generation and deployment, ensuring consistency across the fabric."

Comprehensive and Detailed Explanation From Exact Extract:

Option A: TRUE – state mode shows configuration + operational state.

"The state command provides a unified view of configuration and real-time operational data."

— SR Linux CLI User Guide, "State Mode"

Option B: TRUE – show mode uses predefined templates.

"show commands use structured report templates for consistent operational data display."

— SR Linux CLI User Guide, "Show Commands"

Option C: TRUE – running mode is for configuration changes.

"Configuration edits occur in running mode, which modifies the candidate configuration."

— SR Linux Configuration Fundamentals, "CLI Modes"

Option D: FALSE – use (not enter) switches modes.

"Mode transitions use the use command (e.g., use state). enter navigates hierarchical paths within a mode."

— SR Linux CLI User Guide, "Mode Navigation"

Comprehensive and Detailed Explanation with Exact Extracts:

Option A (Valid): Log sources can be defined using Linux syslog facilities (e.g., local6) and priorities.

Extract from Nokia SR Linux Configuration Guide:

"Log sources are identified using Linux facilities (e.g., kernel, local6) and priorities (e.g., info, error)."

Option B (Valid): The console is a valid source for log messages (e.g., kernel boot logs).

Extract from Nokia SR Linux Fundamentals Guide:

"Console output is treated as a log source, particularly for kernel and early-boot messages captured before system services initialize."

Option C (Valid): SR Linux subsystems (e.g., bgp, system) generate logs with specific priorities.

Extract from Nokia SR Linux Configuration Guide (Section: Log Filters):

"Logs generated by SR Linux subsystems (e.g., network-instance, interface) can be filtered by subsystem name and priority."

Option D (Invalid): "Syslog filter" is not a source—it is a configuration mechanism.

Extract from Nokia SR Linux System Management Guide:

"Filters (/system logging filter) are applied to log sources (facilities/subsystems) to select messages for destinations. Filters themselves do not generate logs."

Comprehensive and Detailed Explanation with Exact Extracts:

Option A is FALSE: SR Linux does not use a simple modulo operation for ECMP hashing. Modulo can lead to uneven distribution and poor resilience. Instead, it uses a more advanced hash algorithm (like CRC32 or murmur) applied to packet header fields (e.g., 5-tuple).

Extract from Nokia SR Linux Configuration Guide (Section: ECMP Configuration):

"The system uses a hash algorithm (e.g., crc32, murmur) over selected fields in the packet header (such as source/destination IP, protocol, source/destination port) to determine the next-hop path. A modulo operation on the hash result relative to the number of paths is not the primary method; the hash space is designed for better spread and minimal disruption."

Option B is FALSE: Resilient ECMP aims for the opposite behavior. Using the same hash seed across routers ensures that a flow taking a specific path on one router will likely take the same corresponding path on downstream routers ("flow stickiness"), preventing localized congestion. Hash buckets map flows to paths consistently network-wide.

Extract from Nokia SR Linux Fundamentals Guide (Section: Resilient Hashing):

"Consistent hash seeds across all routers in the network are critical for resilient ECMP. This ensures that flows hashing to a particular path on an upstream router will hash to the same logical path on downstream routers, maintaining overall traffic distribution and preventing hot-spots."

Option C is FALSE: Using different hash seeds on downstream routers would cause flows following the same path upstream to be randomly distributed downstream, creating potential congestion points ("polarization"). Resilient ECMP requires the same hash seed to be configured consistently across the network for predictable, stable, and congestion-free flow paths.

Extract from Nokia SR Linux Configuration Guide (Section: ECMP Resilient Hashing):

"The hash-seed parameter must be configured identically on all routers within a domain utilizing resilient ECMP. Different seeds cause flow polarization on downstream nodes, defeating the purpose of resilient load balancing and potentially causing link congestion."

Option D is TRUE: This is the core principle of resilient hashing (also called consistent hashing). When a next-hop fails, the hash mapping is recalculated. Only flows that were previously mapped to the failed next-hop need to be remapped to the remaining healthy next-hops. Flows originally mapped to healthy next-hops remain entirely unaffected.

Extract from Nokia SR Linux Fundamentals Guide (Section: Resilient Hashing Benefits):

"A key advantage of resilient hashing is minimal disruption during next-hop failures. When a single next-hop becomes unavailable, only the flows that were hashed to that specific next-hop are affected and need to be rehashed among the remaining next-hops. Flows assigned to other next-hops continue to use their original paths without interruption."

Extract from Nokia SR Linux Configuration Guide (Section: ECMP Resilient Hashing):

"Resilient hashing minimizes the number of flows that need to change paths when the set of next-hops changes (due to failure or addition). This provides greater stability compared to traditional modulo-based hashing, where a topology change can impact a large portion of flows."

Comprehensive and Detailed Explanation From Exact Extract:

Option A: TRUE – SR Linux leverages an unmodified Linux kernel for broad third-party compatibility.

"SR Linux uses a standard, unmodified Linux kernel, enabling seamless integration of third-party applications."

— Nokia SR Linux Technical Overview, "Linux Foundation"

Option B: TRUE – Its state-driven architecture (centered on the Interface Database) enables efficient data access.

"The state-driven architecture provides applications with granular, real-time access to system state via the IDB."

— SR Linux Architecture White Paper, "State-Driven Design"

Option C: TRUE – The NetOps Development Kit (NDK) (not "NetOgs") supports third-party app integration.

"The NetOps Development Kit (NDK) offers tools and libraries for third-party application development and integration."

— SR Linux DevOps Guide, "NDK Overview"

Option D: FALSE – SNMP is not used for CLI access. SR Linux uses gNMI, JSON-RPC, or SSH/CLI.

"SR Linux CLI is accessed via SSH or modern interfaces (gNMI/JSON-RPC). SNMP is supported only for legacy monitoring, not CLI interaction."

— SR Linux Management Interfaces Guide, "Protocol Support"

Conclusion: Option D is incorrect as SNMP is not a CLI access method.

Comprehensive and Detailed Explanation From Exact Extract:

Option A is TRUE: SR Linux is fully model-driven.

"Every configuration and state element in SR Linux is defined by a YANG model."

— SR Linux YANG Data Modeling Guide, "Introduction"

Option B is FALSE: Containers are branches (grouping nodes), and leafs are data components (terminal values). The description is reversed.

"YANG structures data hierarchically: containers organize child nodes (branches), while leafs hold actual data values (e.g., integers, strings)."

— SR Linux YANG Data Modeling Guide, "Tree Structure"

Option C is TRUE: YANG supports JSON/XML encoding.

"YANG models serialize natively to XML or JSON for machine-to-machine communication."

— SR Linux gNMI and JSON-RPC Guide, "Data Encoding"

Option D is TRUE: YANG enables standardized access via gNMI/NETCONF.

"YANG provides a consistent schema for applications to retrieve/configurate data via protocols like gNMI."

— SR Linux Automation Guide, "Model-Driven Interfaces"

Comprehensive and Detailed Explanation From Exact Extract:

Option A: TRUE – MAC-VRF is a Layer 2 instance.

"A MAC-VRF network instance operates as a Layer 2 bridging domain."

— SR Linux Network Instance Guide, "MAC-VRF Overview"

Option B: TRUE – Bridge tables map MACs to egress interfaces.

"The bridge table associates destination MAC addresses with exit interfaces."

— SR Linux Forwarding Guide, "MAC-VRF Forwarding"

Option C: FALSE – MAC-VRF uses MAC addresses (not IP) for forwarding.

"In a MAC-VRF, traffic is switched based solely on destination MAC addresses, not IP."

— SR Linux Network Instance Guide, "Bridging vs Routing"

Option D: TRUE – MAC-VRF groups devices in the same subnet.

"A MAC-VRF instance enables Layer 2 connectivity for devices sharing the same IP subnet."

— SR Linux EVPN Guide, "L2 Network Design"

Conclusion: Option C is false as MAC-VRF is L2-only.

Comprehensive and Detailed Explanation with Exact Extracts:

Option A (TRUE): Type 1 routes enable multi-homing functions.

Extract from Nokia EVPN Multi-Homing Guide:

"Type 1 Ethernet A-D routes signal reachability for an Ethernet Segment (ES) and enable fast convergence/aliasing in multi-homing."

Option B (TRUE): Type 4 routes facilitate DF election.

Extract from Nokia EVPN Fundamentals Guide:

"Type 4 Ethernet Segment routes advertise ESI and VTEP IP to peers for Designated Forwarder (DF) election, which prevents BUM traffic loops."

Option C (FALSE): The ESI is globally unique, not locally significant.

Extract from Nokia SR Linux Configuration Guide (Section: EVPN ESI):

"The ESI must be unique network-wide and consistently configured on all leafs attached to the same multi-homed device. It is not locally significant."

Option D (TRUE): An ES defines the host connectivity model.

Extract from Nokia EVPN Multi-Homing Guide:

"An Ethernet Segment (ES) is a set of links connecting a single host (e.g., server) to one or more leafs for redundancy/load balancing."