Free Practice Questions for Nokia 4A0-D01 Exam

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 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 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 – IP-VRF is defined as a Layer 3 routing instance.

"An IP-VRF network instance provides Layer 3 routing services, isolating tenant routing domains."

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

Option B: TRUE – Forwarding decisions are IP-based.

"IP-VRF forwards packets based on destination IP address using its dedicated routing table."

— SR Linux Routing Guide, "IP-VRF Forwarding"

Option C: TRUE – Each IP-VRF has an independent route table.

"Each IP-VRF maintains a separate route table for complete routing isolation."

— SR Linux Configuration Guide, "Network Instances"

Option D: FALSE – Multiple servers in the same subnet belong to a MAC-VRF (L2 domain), not IP-VRF. IP-VRF handles inter-subnet routing.

"Servers in the same IP subnet must reside in the same MAC-VRF (Layer 2 bridge domain). The IP-VRF provides routing between subnets."

— *SR Linux EVPN Services Guide, "L2/L3 Integration"*

Conclusion: Option D is false because same-subnet devices are grouped in MAC-VRF.

The "baseline diff" command is used to compare the candidate configuration against the baseline datastore to see changes or conflicts, especially when multiple users are involved or to verify differences. It does not indicate that the user is unable to commit changes.

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 – 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: TRUE – Only one management interface (mgmt0) exists.

"The system supports a single management interface (mgmt0) for out-of-band access."

— SR Linux Interface Guide, "Management Port"

Option B: TRUE – Network interfaces bind to hardware ports.

"Network interfaces (e.g., ethernet-1/1) map directly to physical line card ports."

— SR Linux Interface Guide, "Port Mapping"

Option C: FALSE – Loopback interfaces are virtual, not physical.

"Loopback interfaces (e.g., lo0) are logical entities with no physical hardware association."

— SR Linux Routing Guide, "Loopback Interfaces"

Option D: TRUE – L2 parameters (e.g., MTU) are set at the main interface; L3 (e.g., IP) at subinterfaces.

"Layer 2 attributes (MTU, admin-state) are configured under the main interface. Layer 3 settings (IP, VRF) are applied to subinterfaces."

— SR Linux Interface Guide, "Subinterface Configuration"

Comprehensive and Detailed Explanation with Exact Extracts:

Option B is FALSE:

The system-cpu-policer is a software-based policer running on the CPM CPU, not hardware-based.

Extract from Nokia SR Linux QoS Guide (Section: Control Plane Policing):

"The system-cpu-policer is enforced in software on the CPM. In contrast, distributed-policers are hardware-based and execute on line cards."

Other Options are TRUE:

A: Hierarchical policing (e.g., per-protocol child policers under an aggregate) is supported.

Extract: "Hierarchical policers allow aggregate rate-limiting plus per-protocol sub-policers (e.g., for BGP, OSPF)."

C: The system-cpu-policer polices the aggregate traffic reaching the CPM.

Extract: "system-cpu-policer applies to the sum of all traffic forwarded from line cards to the CPM."

D: CPM-filter entries can combine both policers:

distributed-policer (line card hardware) for early per-card rate-limiting.

system-cpu-policer (CPM software) for final aggregate policing.

Extract: "CPM-filter entries may reference both a distributed-policer (for per-line card enforcement) and a system-cpu-policer (for CPM-wide aggregation)."