Nokia Nokia IP Networksand Services Fundamentals 4A0-100 Exam Dumps: Updated Questions & Answers (October 2025)

Spanning Tree Protocol (STP)is used specifically inEthernet Layer 2 networkstoprevent loopscaused byredundant paths.

STPdetects loops and blocks one or more redundant pathsto ensure there is aloop-free topologyin a bridged network.

STP dynamicallyrecalculates the topologyif a link fails, reactivating previously blocked paths.

Explanation of other options:

A. MPLS with LSPs:MPLS uses its own mechanisms for path management, such as RSVP or Segment Routing. STP is not applicable here.

C. OSPF with ECMP (Equal-Cost Multi-Path):OSPF is a Layer 3 protocol that inherently supports multiple paths without loops; STP is not involved.

D. eBGP (Exterior Border Gateway Protocol):Operates at Layer 3 for inter-AS communication; STP is not used in BGP routing.

Therefore,Option Bis correct, as STP is explicitly designed forLayer 2 Ethernet networkswithredundant paths.

Link-State routing protocols(e.g.,OSPF,IS-IS) operate by:

Each routerflooding link-state advertisements (LSAs)throughout the network.

Every router constructs acomplete map of the network topology.

Then each router runs theSPF algorithmto compute optimal paths.

Option C is correct– routers know theentire network topology.

Option A isDistance Vector behavior(e.g., RIP).

Option B isnot efficient or accurate for Link-State.

Option D –hop-countis used inDistance Vector(e.g., RIP).

On theNokia 7750 SR, theControl Processor Module (CPM)includes two compact flash slots,CF1 and CF2, which are used for storing crucial system files. These include:

Runtime software image

Configuration files

Logs and backup configurations

BothCF1 and CF2are used for redundancy and flexibility. Typically, CF1 is designated as the primary storage location for the active software image and configuration, while CF2 serves as a backup. In some configurations, the router can boot from either CF1 or CF2 depending on system settings and availability.

This redundancy is essential for high availability and fast recovery in the event of a failure or manual software update.

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.

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.

TheDHCP client/server exchangefollows a specific four-step sequence known asDORA:

Discover– Client broadcasts to find available DHCP servers.

Offer– DHCP server responds with an IP address offer.

Request– Client requests the offered IP.

Acknowledgement– Server confirms the lease.

This ensuresdynamic IP configurationand is used in enterprise and home networks.

VPLS (Virtual Private LAN Service)is aLayer 2 VPN servicethat emulates abridged Ethernet LANacross an MPLS/IP network.

Learns MAC addresses dynamically from:

SAPs (Service Access Points)

SDPs (Service Distribution Points)

Maintains aForwarding Database (FDB)per VPLS instance.

For unknown MAC destinations, a VPLSfloods the frameto all other sites – just like a regular Ethernet switch.

Option C is FALSE– VPLSdoes NOT discard unknown MACs; itfloodsthem.

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.

ICMP (Internet Control Message Protocol)is used for network diagnostics and error messaging. Key uses include:

Ping (Echo Request/Reply)– tests end-to-end connectivity✔

Traceroute– uses ICMP time exceeded messages to identify hops✔

Error reporting– returns various error types with differentcodes✔

However,ICMP does not re-route traffic. If a destination is unreachable, ICMP reports the error back to the sender; it doesn’t instruct routers to re-route.

Option D is FALSE– ICMPdoes not perform routing.

BGP (Border Gateway Protocol)uses amulti-step decision processto select the best route among multiple paths. It doesnot use SPF or simple metrics like hop count.

Key BGP selection criteria include:

Local preference

AS path length

Origin type

MED (Multi-Exit Discriminator)

eBGP over iBGP

IGP metric to next hop

Option C is correct– BGP evaluatesmultiple attributesfor route selection.