Free Nokia 4A0-D01 Practice Exam with Questions & Answers

Comprehensive and Detailed Explanation with Exact Extracts:

Options A, B, and C describe standard leaf-spine eBGP operation:

Leaf routers peer with spines (eBGP), advertising local prefixes (Option C).

Spines learn prefixes from leaves (Option B) and re-advertise them to other leaves (Option A).

Extract from Nokia Data Center Fabric Guide (Section: eBGP Leaf-Spine):

"Leaf routers establish eBGP sessions with spine routers, advertising prefixes of locally attached endpoints. Spine routers propagate these prefixes to all other leaf routers, providing full connectivity."

Option D is FALSE: Leaf routers do not peer directly with each other in standard designs. They communicate via spines.

Extract from Nokia Data Center Fabric Guide (Section: Routing Design):

"Leaf routers never establish direct eBGP sessions with other leaf routers. All inter-leaf communication occurs via spine routers, which act as route reflectors or forwarding hubs."

Comprehensive and Detailed Explanation with Exact Extracts:

Exhibit Analysis:

The configuration defines a log file named bgp-log (not a buffer) under system logging.

It includes messages from subsystems bgp and netinst (network-instance).

SR Linux Logging Command Syntax:

show system logging file  is the operational command to display contents of a log file.

show system logging buffer  is used for memory buffers, not files.

info commands display configuration, not log contents.

Verification from Documentation:Extract from Nokia SR Linux CLI Guide (Section: Logging Commands):

"Use show system logging file  to display the current contents of a configured log file. For example:

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A:dc-leaf-1# show system logging file bgp-log

This outputs the log entries stored in the specified file."

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

"Log files are persistent entities stored in /var/log/srlinux/. Their contents are viewed exclusively via show system logging file, not info or buffer commands."

Why Other Options Are Incorrect:

A: buffer references in-memory logs, not persistent files.

C/D: info displays configuration (e.g., info system logging shows the snippet in the exhibit), not log contents.

Comprehensive and Detailed Explanation From Exact Extract:

In a leaf-spine Clos network:

Option A is TRUE: Each leaf connects to every spine for full redundancy and non-blocking fabric.

"In a Clos topology, every leaf node connects to every spine node, ensuring any-to-any connectivity."

— Nokia Data Center Fabric Design Guide, "Leaf-Spine Architecture"

Option B is TRUE: East-west traffic flows predictably via spines.

"Leaf-spine provides deterministic paths for east-west traffic, minimizing latency and jitter."

— Nokia SR Linux EVPN Configuration Guide, "Traffic Flow in Clos Networks"

Option C is FALSE: Clos networks do not use STP. They rely on Layer 3 ECMP and routing protocols for loop avoidance.

"Clos fabrics eliminate STP by design. Forwarding loops are avoided through ECMP and routing protocols (e.g., BGP), not Layer 2 STP."

— Nokia Data Center Fabric Best Practices, "Loop Avoidance"

Option D is TRUE: ECMP load-balances traffic across multiple spine paths.

"ECMP is fundamental to leaf-spine, distributing traffic across all available spine links."

— Nokia SR Linux Routing Guide, "ECMP in Clos Fabrics"

Comprehensive and Detailed Explanation From Exact Extract:

Option A: TRUE – Fabric intent is declaratively defined in YAML.

"FSS uses YAML-based declarative intent to define and manage fabric configurations."

— Nokia Fabric Services System User Guide, "Intent-Based Fabric"

Option B: FALSE – The Digital Sandbox is for pre-deployment validation, not performance monitoring.

"The Digital Sandbox simulates configurations for validation before deployment. Performance monitoring is handled by telemetry analytics, not the sandbox."

— Nokia FSS Deployment Guide, "Digital Sandbox"

Option C: TRUE – Telemetry is contextualized with intent.

"Telemetry data is correlated with fabric intent, providing context-aware insights."

— Nokia FSS Operations Guide, "Telemetry and Analytics"

Option D: TRUE – FSS is cloud-native for flexible integration.

"FSS’s cloud-native microservices architecture simplifies integration with customer ecosystems."

— Nokia FSS Architecture White Paper, "Cloud-Native Design"

Conclusion: Option B misrepresents the Digital Sandbox’s purpose.

Comprehensive and Detailed Explanation From Exact Extract:

Option A: TRUE – "duplicate" status confirms multiple interfaces.

"A 'duplicate' entry indicates the MAC was detected on multiple ports."

— SR Linux Bridge Table Guide, "Duplicate MAC Handling"

Option B: FALSE – No re-learning rate data is present. The output shows a static duplicate entry, not rate violations.

"MAC re-learning rate thresholds generate specific alerts (not shown here). This exhibit only shows a persistent duplicate state."

— SR Linux Monitoring Guide, "MAC Mobility Events"

Option C: TRUE – The MAC is explicitly bound to ethernet-1/10.0.

"The 'Destination' column specifies the interface where the MAC was last observed."

— SR Linux CLI Reference, "show bridge-table"

Option D: TRUE – Duplicate detection is active since duplicates are flagged.

"The presence of 'duplicate' entries confirms MAC duplication detection is enabled."

— SR Linux Security Guide, "MAC Duplication"

Conclusion: Option B is unsupported by the exhibit.

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:

LLDP (Link Layer Discovery Protocol) frames are link-local multicast frames sent to the destination MAC address 01:80:C2:00:00:0E. They are not routed (eliminating Option D) and operate independently of VRF tables (eliminating Options A/B). SR Linux floods LLDP frames periodically on all active interfaces.

Exact Extract:

*"LLDP frames are transmitted periodically as untagged Ethernet frames to the nearest-bridge multicast address (01:80:C2:00:00:0E). They are flooded locally and not forwarded beyond the local subnet."*

Comprehensive and Detailed Explanation with Exact Extracts:

Options A, B, and C ARE configured in static-routes:

Blackhole: Configured under static-routes for a prefix to drop traffic.

IPv4 destination prefix: Defined directly in the static-routes container.

Preference value: Set per static route entry within static-routes.

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

"Static routes are configured under /routing-policy/static-routes. Each entry requires a prefix (e.g., 0.0.0.0/0). The blackhole parameter and preference value are configured directly within this container for a specific prefix."

Option D (Next-hop group) CANNOT be configured in static-routes:

Next-hop groups are separate objects defined under /routing-policy/next-hop-groups.

The static-routes container references a next-hop group by name but does not define its properties.

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

"Next-hop groups are configured under /routing-policy/next-hop-groups. Each group is given a name and defines properties like next-hop IPs, blackhole behavior, or indirect settings. Static routes reference a next-hop group via the next-hop-group parameter under /routing-policy/static-routes but do not configure the group itself here."

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 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"