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

Comprehensive and Detailed Explanation with Exact Extracts:

Options A, B, and C are Day 2+ operations:

A: Telemetry enables real-time monitoring.

B: Health analysis supports proactive maintenance.

C: Sandbox validates changes pre-deployment.

Extract from Nokia FSS Day 2 Operations Guide:

"Day 2+ includes telemetry-based monitoring, health analytics, and sandbox testing for upgrades/changes."

Option D is a Day 0 activity:

Fabric intents define initial design templates (Day 0), not ongoing operations.

Extract from Nokia FSS Lifecycle Management Guide:

"Fabric intents are used during Day 0 design to build templates. Day 2+ focuses on operational tasks like monitoring (A), health checks (B), and sandbox validation (C)."

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 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:

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 From Exact Extract:

BGP is widely adopted in data center fabrics due to its scalability, multiprotocol support, and maturity. However, option B is incorrect because BGP does not automatically discover neighbors. Unlike link-state protocols (e.g., OSPF, IS-IS), which use multicast for neighbor discovery, BGP requires manual configuration of peers via IP addresses. This is explicitly stated in Nokia's documentation:

"BGP requires explicit configuration of neighbors. It does not support automatic neighbor discovery via multicast/broadcast mechanisms."

— Nokia SR Linux Configuration Guide, Section: "BGP in Data Center Underlays"

Validation of Other Options:

A: Correct. BGP scales more efficiently in large data centers than link-state protocols. Per Nokia:

"BGP’s path-vector design reduces control-plane overhead compared to link-state protocols, making it optimal for large-scale data center underlays."

— Nokia Data Center Fabric Design Guide

C: Correct. BGP’s maturity is a key advantage:

"BGP’s decades of deployment and extensive vendor interoperability make it a reliable choice for fabric underlays."

— SR Linux EVPN Services Guide

D: Correct. BGP natively supports multi-protocol extensions (MP-BGP) for IPv4/IPv6:

"MP-BGP enables simultaneous transport of IPv4 and IPv6 routes via the same BGP session."

— SR Linux Routing Protocols Handbook

Conclusion:

Option B is the only choice that misrepresents BGP functionality, as neighbor auto-discovery is not a feature of BGP. This distinction is critical in Nokia SR Linux fabric deployments.

Comprehensive and Detailed Explanation with Exact Extracts:

Options A, B, and C are TRUE:

A: BFD detects microsecond-level link failures, faster than BGP timers.

B: BFD negotiates a control-packet rate during session setup.

C: Missed BFD packets trigger a session-down event, notifying BGP.

Extract from Nokia SR Linux Configuration Guide (Section: BFD for BGP):

"BFD provides sub-second failure detection. Peers negotiate tx-interval and rx-interval timers dynamically. If the configured multiplier threshold of missed packets is reached, BFD notifies BGP to tear down the session."

Option D is FALSE: BFD does not modify BGP’s update timers (e.g., min-advertisement-interval). It only accelerates failure detection.

Extract from Nokia SR Linux Fundamentals Guide (Section: BFD Integration):

"BFD does not influence BGP’s route advertisement or withdrawal timers. It solely enhances failure detection speed, allowing BGP to react faster to topology changes."

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: 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 with Exact Extracts:

Option A is FALSE: The provisioning script URL is not defined in the TLS profile. It is provided via DHCP (option 239) or DNS.

Extract from Nokia SR Linux ZTP Guide:

"The DHCP server supplies the URL to the provisioning script (via option 239). TLS profiles secure script/image downloads but do not define the script location."

Options B, C, and D are TRUE:

B: ZTP is managed by the ztp application in the management container.

C: DHCP provides initial IP/gateway.

D: ZTP requires no manual configuration.

Extract from Nokia SR Linux Installation Guide:

"The ZTP application automates deployment. It uses DHCP for network parameters and fetches scripts to make the device operational without pre-configuration."

Comprehensive and Detailed Explanation From Exact Extract:

Option A: TRUE – IP addresses are assigned to IRB subinterfaces.

"The IRB subinterface configuration includes the IP address for integrated routing."

— SR Linux EVPN Guide, "IRB Configuration"

Option B: TRUE – IRB subinterfaces reside in IP-VRF instances.

"IRB subinterfaces are associated with an IP-VRF network instance for L3 routing."

— SR Linux Network Instance Guide, "IP-VRF Setup"

Option C: FALSE – One IRB subinterface serves an entire MAC-VRF (L2 domain), not per interface.

"A single IRB subinterface provides L3 gateway services for all interfaces in a MAC-VRF instance."

— SR Linux EVPN Guide, "Asymmetric IRB Design"

Option D: TRUE – Each MAC-VRF uses one IRB subinterface.

"Each MAC-VRF network instance requires exactly one IRB subinterface for inter-subnet routing."

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