4A0-100 Nokia IP Networksand Services Fundamentals Free Practice Exam Questions (2025 Updated)

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

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.

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.

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

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.​

VPWS (Virtual Private Wire Service)on Nokia 7750 SR:

Emulates aLayer 2 point-to-pointconnection.

Does not require MAC learning, unlike VPLS.

UsesMPLS encapsulation,not IP datagramsfor transport.

Option D is FALSE– VPWS usesMPLS labels, not IP encapsulation.

A layered protocol stack is designed to simplify network communication by separating functionalities into distinct layers. Each layer has a defined role and communicates with the layers directly above and below it. The main benefits of this model include:

Simplified design and implementation: Developers can focus on one layer without needing to understand the entire system.

Flexibility: New protocols can be developed and inserted at specific layers without redesigning the whole stack.

Interoperability: Standard interfaces allow different systems and vendors to work together.

Isolation of functions: Errors and updates can be managed within one layer without impacting others.

However,reducing protocol overhead is not a primary goalof this model. In fact, the encapsulation and interaction between layers can sometimesintroduce extra overhead. This overhead is a trade-off accepted to gain the other benefits listed above.

In Nokia SR OS:

Aphysical interfacerefers to a physical port on the router (e.g., port 1/1/1).

It can be configured withIP addresses, associated with services (e.g., IES, VPRN), and connects to other routers or customer devices.

Systemandloopbackinterfaces arelogical interfaces, not physical.

Option D is FALSE, because a physical interfacecannotbe of type "system" or "loopback" — those arevirtual/logicalinterfaces in the Nokia router architecture.

Ahubis aphysical layer (Layer 1)networking device used to connect multiple Ethernet devices in a network. Unlike switches or routers, hubs donot inspect or process frame headers. Instead, they perform a simple task:

Receive a signal (electrical or optical) on one port

Replicate that signal identically to all other ports

This means the hubdoes not examine Layer 2 (MAC addresses) or Layer 3 (IP addresses)and doesnot perform intelligent forwarding. It merelybroadcasts all incoming traffic to every other connected device, often resulting inhigh collision domainsand poor efficiency.

Option Adescribes arepeater, not a hub.

Option Cdescribes aswitch(Layer 2 device).

Option Ddescribes arouter(Layer 3 device).

Option Bis correct: A hub does not inspect headers and replicates traffic blindly.

TheIngress Label Edge Router (LER)is the first router that:

Receives an unlabeled IP packet.

Applies an MPLS labelbased on its forwarding decision.

Forwards it into theMPLS core.

Option A is correct– Ingress LER does MPLS label push.

Option B (Egress LER)– removes labels at the end of the path.

Option C (LSR)– switches labels, but doesn’t push them onto unlabeled packets.

Option D– is not a specific MPLS role.

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.