Free Practice Questions for Nokia 4A0-100 Exam

Question 1

Which of the following is a characteristic of a subnet created with a /31 prefix?

AThere is no broadcast address on the network.

BThe address is only used as a loopback address.

CThis specifies a single host address.

DThe address is only used for router IDs.

Correct Answer: A. There is no broadcast address on the network.

Explanation:

A /31 subnet in IPv4 provides exactly two IP addresses (e.g., 192.168.1.0/31 usable: 192.168.1.0 and 192.168.1.1). Traditionally, these would represent a network address and a broadcast address, but RFC 3021 redefines /31 subnets for point-to-point links, such as router-to-router connections.

In a /31 subnet:

Broadcast address is not used.

Both IPs are treated as usable host addresses.

It's ideal for point-to-point links, saving address space.

This is widely supported and standardized in Nokia IP and routing platforms.

Nokia IP Fundamentals Guide -- Subnetting Techniques

RFC 3021 -- 'Using 31-Bit Prefixes on IPv4 Point-to-Point Links'

Question 2

In an MPLS network, which device is responsible for taking an unlabeled packet and encapsulating it with an MPLS label?

AIngress Label Edge Router

BEgress Label Edge Router

CLabel Switching Router

DNext-hop Router

Correct Answer: A. Ingress Label Edge Router

Explanation:

The Ingress Label Edge Router (LER) is the first router that:

Receives an unlabeled IP packet.

Applies an MPLS label based on its forwarding decision.

Forwards it into the MPLS core.

Option A is correct -- Ingress LER does MPLS label push.

Option B (Egress LER) -- removes labels at the end of the path.

Option C (LSR) -- switches labels, but doesn't push them onto unlabeled packets.

Option D -- is not a specific MPLS role.

Nokia IP/MPLS Fundamentals Guide -- Label Operations

RFC 3031 -- MPLS Architecture

Question 3

Which of the following statements about the OSPF routing protocol is FALSE?

AIt is a link state protocol.

BIt supports hierarchy using multiple areas.

CIt uses a mechanism for routers to exchange topology information.

DIt uses hop-count for route selection.

Correct Answer: D. It uses hop-count for route selection.

Explanation:

OSPF (Open Shortest Path First) is a Link-State protocol that uses:

Cost (based on bandwidth) as its metric.

Dijkstra's algorithm to compute shortest path trees.

Supports hierarchical routing with areas (e.g., Area 0 as backbone).

Routers exchange LSAs, not full routing tables.

Option D is FALSE -- OSPF does not use hop-count. That's a RIP (Distance Vector) feature.

Nokia IP Routing Guide -- Section: ''OSPF Operation and Area Design''

RFC 2328 -- OSPFv2 Protocol Specification

Question 4

Which tier of Internet service providers provides transit services to other ISPs?

ATier 1 and Tier 2 ISPs

BTier 1 and Tier 3 ISPs

CTier 2 and Tier 3 ISPs

DTier 3 ISP

Correct Answer: A. Tier 1 and Tier 2 ISPs

Explanation:

Tier 1 ISPs: Have global reachability and exchange traffic via peering. They do not pay for transit.

Tier 2 ISPs: Purchase transit services from Tier 1 and provide transit to Tier 3 or other Tier 2 ISPs.

Tier 3 ISPs: Provide last-mile connectivity to end users and do not provide transit services.

Option A is correct -- Tier 1 and Tier 2 provide transit services.

Nokia IP Networks and Services Guide -- ISP Tiering

Global Internet Infrastructure Overview

Question 5

Which of the following statements about MD-CLI is FALSE?

A. It allows atomic transactions. B. Configuration changes are activated when the running configuration datastore is saved to a file. C. To achieve transactional configuration, it is necessary to have multiple configuration datastores. D. Multiple users may enter the global configuration mode concurrently.

AIt allows atomic transactions -- True. MD-CLI uses atomic transactions to apply multiple changes at once, ensuring consistency and rollback if a failure occurs.

BConfiguration changes are activated when the running configuration datastore is saved to a file -- False. In MD-CLI, changes are committed to the running datastore when a user issues the commit command, not when saving to a file. Saving to a file is a separate action (e.g., admin save) and does not trigger configuration activation.

CTo achieve transactional configuration, it is necessary to have multiple configuration datastores -- True. MD-CLI uses candidate, running, and operational datastores to implement transaction-based configuration.

DMultiple users may enter the global configuration mode concurrently -- True. MD-CLI supports multi-user access to global configuration with locking mechanisms to prevent conflicts.

Correct Answer: B. Configuration changes are activated when the running configuration datastore is saved to a file -- False. In MD-CLI, changes are committed to the running datastore when a user issues the commit command, not when saving to a file. Saving to a file is a separate action (e.g., admin save) and does not trigger configuration activation.

Explanation:

The Model-Driven Command Line Interface (MD-CLI) in Nokia SR OS provides a structured and programmatic way to manage configurations. It is based on a transactional model, meaning changes are made in a candidate configuration before being committed to the running configuration.

Let's review each statement:

Nokia SR OS MD-CLI User Guide

Nokia SRA Study Guide -- Chapter: 'Model-Driven Configuration and Transactions'

Question 6

Which of the following statements about the IP forwarding process on a router is TRUE?

AIt uses the routing table to find a match for the source IP address.

BIt uses the routing table to find a match for the destination IP address.

CIt uses the ARP table to find a match for the source MAC address.

DIt uses the ARP table to find a match for the destination MAC address.

Correct Answer: B. It uses the routing table to find a match for the destination IP address.

Explanation:

When a router forwards a packet, it performs the following operations:

Looks up the destination IP address in the routing table to determine the next hop or egress interface.

Uses the ARP table to resolve the MAC address of the next-hop IP.

Option A is incorrect -- source IP is not used for route lookup.

Option C is incorrect -- routers don't resolve the source MAC.

Option D is partially true, but routing begins with the routing table, making B the most accurate.

Nokia IP Fundamentals Study Guide -- Chapter: ''IP Packet Forwarding''

RFC 1812 -- Requirements for IP Routers