4A0-100 Nokia IP Networksand Services Fundamentals Questions and Answers

In MPLS architecture, theIngress LER (Label Edge Router)is responsible for:

Pushing labelsonto unlabeled packets and injecting them into the MPLS domain.

Acting as thestarting point of the Label Switched Path (LSP).

From the diagram:

R1is thestarting point (Ingress LER)for both LSP A and LSP B.

R4is theEgress LER, which wouldpopthe labels at the end of the LSP.

So,R1 is responsible for label push (imposing)at the start of both LSPs.

Option A is correct– R1 pushes labels for both LSP A and LSP B.

Option Bis incorrect – R4 is an egress router, not ingress.

Option C/Dare incorrect – the LSPs both start at R1.

Abroadcast IP addressis used tosend a message to all deviceson a specific IP subnet. This address is thehighest address in the subnet(i.e., all host bits set to 1).

Example: In 192.168.1.0/24 → broadcast is 192.168.1.255.

It is used for purposes like ARP requests or DHCP discovery.

Option A is correct– refers to all hosts in a subnet.

Option Brefers tomulticast, not broadcast.

Option Cmight refer toanycast, which is different.

Option Ddescribes aunicastaddress.

A/31 subnetin IPv4 provides exactlytwo IP addresses(e.g., 192.168.1.0/31 → usable: 192.168.1.0 and 192.168.1.1). Traditionally, these would represent anetwork address and a broadcast address, butRFC 3021redefines /31 subnets forpoint-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'sideal for point-to-point links, saving address space.

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

Route summarization (a.k.a. supernetting)is the process ofcombining multiple contiguous subnetsinto asingle summarized route, which:

Reduces routing table entries

Enhances scalability and efficiency

Minimizes instability by localizing route changes

Option A is falsebecauseit describes subnetting, not summarization. Summarization works in theopposite direction– combining smaller routes into a larger one.

AP router (Provider router)is locatedin the core of the service provider’s network. Its functions include:

ForwardingMPLS-labeled packetsbetweenPE routers.

Not interacting directly with customer routes or routing instances.

Having no knowledge ofVPN routing or customer-specific services.

Option C is correct– P routers sit in theMPLS core, isolated from customer edge.

In Nokia SR OS, event logging allows the router to report system events, alarms, and operational changes to external systems or users. The valid logging destinations include:

SNMP– Used to send traps or informs to SNMP managers.

Syslog– Sends logs to centralized syslog servers, a standard for log management.

NETCONF– Can be used for event notification in model-driven management setups, although it is more frequently used for configuration and state management.

However,BOF (Boot Options File)isnota valid logging destination. TheBOFis used to store critical system boot configurations, such as:

Which image to boot from

Network interface settings

Auto-boot parameters

BOF plays no role in the logging infrastructure.

A Virtual Private Network (VPN) is designed to provide secure and private communication over a shared or public infrastructure. Key characteristics of VPNs include:​

Traffic Isolation:Each customer's traffic is kept separate from others, ensuring privacy and security.​

Shared Infrastructure:Service providers can support multiple VPNs over the same physical infrastructure, optimizing resource utilization.​

Customization:VPNs can be tailored to meet the specific requirements of individual customers, including security policies, routing, and quality of service.​

However,customer data is not alteredas it traverses a VPN. Instead, VPNs employ encryption and tunneling protocols to protect data integrity and confidentiality during transmission. The primary goal is to ensure that data remains unchanged and secure from end to end.​

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

Let's review each statement:

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

B. Configuration changes are activated when the running configuration datastore is saved to a file–❌False. In MD-CLI, changes are committed to therunning datastorewhen 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 doesnot trigger configuration activation.

C. To achieve transactional configuration, it is necessary to have multiple configuration datastores–✔True. MD-CLI usescandidate,running, andoperationaldatastores to implement transaction-based configuration.

D. Multiple users may enter the global configuration mode concurrently–✔True. MD-CLI supportsmulti-user accessto global configuration with locking mechanisms to prevent conflicts.

TheNokia 7750 SR architectureseparates its operations intocontrol planeanddata planefunctions.

TheData Planeincludes hardware components responsible for forwarding traffic at line rate. These components include:

MDA (Media Dependent Adapter)– interfaces with physical media.

IOM (Input/Output Module)– performs high-speed packet forwarding and processing.

XMA (eXpandable Media Adapter)– extends port capacity and media support.

TheControl Planeincludes theCPM (Control Processor Module), which is responsible for running routing protocols, managing configuration, system operations, and other control-related functions. The CPM does not participate in data forwarding and is thusnot part of the data plane.