Nokia 4A0-100 Nokia IP Networksand Services Fundamentals Exam Practice Test

VLAN Stacking, also known asQ-in-Q tunneling, is a technology that allowsmultiple customers to use overlapping VLAN IDswhile being transported over ashared service provider network.

Key Concepts:

Customer VLAN (C-VLAN):The VLAN used by the customer in their own network.

Service VLAN (S-VLAN):The VLAN used by the service provider to encapsulate the customer VLAN.

When VLAN stacking is applied:

A customer's Ethernet frame already tagged with aC-VLANisencapsulated with an additional outer S-VLAN tag.

This way,multiple customers can use the same C-VLAN ID, but remain isolated by theunique S-VLANassigned to them by the service provider.

Why Other Options Are Incorrect:

A. VLAN Trunking:Used to carry multiple VLANs over a single physical link but doesn’t allow reuse of VLAN IDs across customers.

C. VLAN Tagging:Refers to the general process of adding a VLAN tag; it doesn't provide the isolation needed across shared infrastructure.

D. VLAN Routing:Refers to Layer 3 routing between VLANs, not to ID reuse or transport over a shared provider backbone.

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.

➡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

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

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.

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.

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.

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.

TheInternet Assigned Numbers Authority (IANA)is responsible for managing theglobal IP address pool, along with:

Allocating blocks ofIP addresses to Regional Internet Registries (RIRs)such as ARIN (North America), RIPE NCC (Europe), APNIC (Asia-Pacific), etc.

Managingautonomous system numbers (ASNs).

OverseeingDNS root zonesand protocol parameters.

IANAdoes not assign IPs directly to enterprises or individuals— those tasks are delegated toRIRs and ISPs.

Option A & B:Enterprises and residential allocations are handled by ISPs or RIRs.

Option D:North American IPs are managed byARIN, not IANA.

Option C is correct– IANA manages theglobal IP address allocationhierarchy.

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.

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.

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