Nokia 4A0-100 - Nokia IP Networksand Services Fundamentals

When a routerforwards a packet, it performs the following operations:

Looks up the destination IP addressin therouting tableto determine thenext hoporegress interface.

Uses theARP tableto resolve theMAC address of the next-hop IP.

Option Ais incorrect – source IP is not used for route lookup.

Option Cis incorrect – routers don’t resolve thesource MAC.

Option Dis partially true, butrouting begins with the routing table, makingBthe most accurate.

TheShortest Path Tree (SPT)is calculated byLink-State routing protocolslikeOSPFandIS-ISusing:

Acomplete map of the network topology.

Each router uses algorithms likeDijkstra’sto compute the shortest paths to all destinations.

Option C is correct– fullnetwork topologyis used.

Option Arefers to Distance Vector methods.

Option BandDare results of topology analysis but not the input used.

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.

Astatic routeis a manually configured route added by a network administrator. It does not rely on dynamic routing protocols or metrics.

Itdoes not exchangeroutes with other routers (A – false).

It can be used bothwithin or across ASes(B – false).

Itdoes not use metricslike hop count (C – false).

Option D is correct– the operator explicitly defines the next-hop IP or egress interface manually.

Static routes are often used for:

Default routing

Backup routing

Simple or small networks

A/26 subnetmeans26 bits for the networkand6 bits for host addressing(32 - 26 = 6):

2⁶ = 64 total addresses per subnet

64 - 2 =62 usable host addresses per subnet

/24 to /26 increases subnet bits by 2, so:

2² =4 subnetsfrom one /24

But the question asks aboutusing /26, which means:

From /24 → each /26 block gives64 IPs

So you get4 subnets total

But the options must be interpreted carefully!

→Let's calculate again properly:

/26 = 64 addresses per subnet (2⁶)

Usable hosts per subnet = 64 - 2 = 62

Number of subnets in /24 when divided by /26 = 2^(26 - 24) = 4 subnets

So correct result is:

4 subnets, 62 hosts per subnet→Correct Answer: C

However,Option D says 8 subnets, 30 hosts per subnet, which actually matches a/27 mask, not /26.

Final Correct Answer:C

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.

In the diagram:

R2 and R4 areboth within AS 65540, which indicates that they are in thesame Autonomous System.

eBGP (External Border Gateway Protocol)is designed for routingbetween different ASes(inter-AS routing).

Since R2 and R4 are in thesame AS, you would use:

OSPForIS-IS(both interior gateway protocols – IGPs)✔

Static routingis also valid between any two routers if manually configured✔

eBGP❌is invalid between routersin the same AS.

âž¡The correct protocol in that case would beiBGP (internal BGP)if BGP were to be used within the AS.

Therefore, the correct answer is: D. eBGP

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.

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).