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

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.

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).

In Nokia SR OS, theMD-CLIprovides multiple configuration edit modes to allow different types of user interaction with the configuration system:

Private modeallows multiple users to create individual configuration candidates, which are then merged with the global candidate during commit.

Global modeenables multiple users to edit the same candidate configuration at the same time, with a shared commit session.

Read-only modeallows the user to view the configuration without making changes.

Exclusive moderestricts access to the global candidate configuration such thatonly one user at a timecan enter and make changes. This prevents conflicts and is useful in environments where strict control over configuration changes is necessary.

Therefore, the correct answer isExclusive mode, as itexclusively locks access to the global candidatefor a single user.

Address summarization(also called route aggregation) is a technique used in IP routing to combine several contiguous network prefixes into asingle summarized route.

This reduces the number of routes that need to be advertised and stored in routing tables, improvingscalability and performance.

Option A is correct– summarization replaces many specific routes with a single aggregated route.

Option Brefers to best path selection (not summarization).

Option Cis incorrect; duplicate advertisements are still processed and filtered based on metrics.

Option Dis unrelated to summarization; directly connected routes are always advertised unless specifically filtered.

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.

Abroadcast domainis a logical division of a network in which all nodes can reach each other with broadcast frames (Layer 2). Devices within the same broadcast domain receive broadcast packets sent by others.

In the diagram:

Multiple users connect tohubs.

Hubs are Layer 1 devices anddo not break broadcast domains. They simply replicate incoming electrical signals to all ports.

Hubs are then connected toswitches.

Switches, unless VLANs are configured,forward broadcasts to all ports except the incoming one, effectively keeping all devices in the same broadcast domain.

The two switches are connected together without VLAN segmentation.

Therefore:

The entire LAN depicted isa single Layer 2 broadcast domain.

There areno routers or VLANsto break or separate the domain.

Correct answer: A. 1

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.

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.

Thesystem interfacein Nokia SR OS is aloopback-style logical interfacethat represents therouter itself. It is used for:

Router ID assignment (if not manually set)

Source IP for control-plane protocols (OSPF, BGP)

Reachability testing

Important properties:

It istype loopback✔

Itexists by default✔

If router ID is unset, it uses thesystem IP address✔

Butthe IP address on the system interfacedoes not need to be /32❌

It can haveother prefix lengths, especially in service provider scenarios.

Thus, Option B is FALSE.