Nokia 4A0-105 Practice Test Questions, Exam Dumps

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4A0-105 Nokia Practice Test Questions and Exam Dumps

Question No 1:

Which of the following technologies allows for two explicit VLAN tags to be received from a customer device?

A. RSVP-TE
B. SP-VLAN
C. QinQ
D. Dot1Q

Answer: C

Explanation:

The correct technology that allows for two explicit VLAN tags to be received from a customer device is QinQ.

Here's why:

A (RSVP-TE): RSVP-TE (Resource Reservation Protocol with Traffic Engineering) is a protocol used in MPLS networks for reserving bandwidth and ensuring specific paths for traffic engineering. It is not related to VLAN tagging and does not deal with VLAN tag handling. Therefore, it is not the correct answer.
B (SP-VLAN): SP-VLAN (Service Provider VLAN) is not a standard technology for handling VLAN tags. It is a term that might be used in some contexts to refer to VLANs used by service providers, but it doesn't specifically address the dual-tagging of VLANs. Therefore, this option is not correct.
C (QinQ): QinQ (802.1Q-in-802.1Q) is a technology that allows the encapsulation of one VLAN tag inside another VLAN tag. This allows a service provider network to carry multiple VLANs from customers (often referred to as VLAN stacking). With QinQ, a customer can send two explicit VLAN tags — one for the customer’s VLAN and another for the service provider’s VLAN. This is commonly used in provider bridges and Metro Ethernet networks to segregate traffic and avoid VLAN collision. QinQ is the correct answer because it allows for two VLAN tags to be received from a customer device.
D (Dot1Q): Dot1Q is the IEEE standard for VLAN tagging, and it allows for a single VLAN tag to be applied to Ethernet frames. It doesn't support receiving two VLAN tags from a customer device. Dot1Q is often used for trunking and carrying multiple VLANs over a single link, but it doesn't handle multiple explicit VLAN tags (as QinQ does). Therefore, it is not the correct answer.

In summary, QinQ is the technology that allows for two explicit VLAN tags to be received from a customer device, making C the correct answer.

Question No 2:

What is the SA in the Ethernet frame used for by a layer 2 switch?

A. MAC learning
B. SA filtering
C. Routing table population
D. Frame forwarding

Correct Answer: A

Explanation:

The Source Address (SA) in an Ethernet frame is used by a Layer 2 switch for MAC learning. Let’s break down the function of the SA and the options:

A. MAC Learning:

This is the correct answer. A Layer 2 switch uses the Source Address (SA) in the Ethernet frame to learn the MAC address of the device that sent the frame. The switch records the MAC address and the port on which it received the frame in its MAC address table. This allows the switch to associate specific devices with their respective ports, enabling it to forward frames to the correct destination port efficiently.

B. SA Filtering:

SA filtering is not a typical function of a Layer 2 switch. A Layer 2 switch does not generally filter or block frames based on their Source Address. It mainly uses the Source Address for MAC learning and forwarding frames based on destination addresses.

C. Routing Table Population:

This option is incorrect. Routing tables are used by Layer 3 devices (routers) to route packets based on IP addresses, not by Layer 2 switches, which operate based on MAC addresses. A Layer 2 switch does not use the Source Address (SA) to populate routing tables.

D. Frame Forwarding:

While frame forwarding is indeed a key function of a Layer 2 switch, it is done using the Destination Address (DA) in the Ethernet frame, not the Source Address (SA). The switch forwards the frame based on the DA and its MAC address table, not directly on the SA.

The Source Address (SA) in an Ethernet frame is primarily used by a Layer 2 switch for MAC learning (Option A), where the switch learns and stores the MAC address associated with each port for future frame forwarding decisions.

Question No 3:

What are the limitations of a traditional layer 2 switch? (Choose 3)

A. Isolates collision domains.
B. Requires layer 2 loop prevention.
C. Slow response to topology changes.
D. Limited to 4094 VLANs per switch.
E. Increased flooding.

Correct answer: B, C, E

Explanation:

Traditional Layer 2 switches operate at the data link layer and are designed primarily to forward traffic based on MAC addresses. While they perform basic switching operations efficiently, there are some inherent limitations due to the nature of Layer 2 technology. Let's break down the options:

Option A: Isolates collision domains.

This is not a limitation of a Layer 2 switch; in fact, this is one of the advantages of Layer 2 switches. A traditional Layer 2 switch isolates collision domains by using each port as a separate collision domain. This allows for better efficiency and reduces collisions in the network compared to hubs, which have a single collision domain for all devices.

Option B: Requires layer 2 loop prevention.

This is a limitation of Layer 2 switches. Without proper loop prevention mechanisms, such as Spanning Tree Protocol (STP), Layer 2 switches can create broadcast loops, which can lead to network instability, flooding, and high CPU usage. This requires Layer 2 loop prevention to maintain network stability.

Option C: Slow response to topology changes.

This is another limitation of traditional Layer 2 switches. When network topology changes occur (e.g., a switch is added or a link fails), the Layer 2 switches can experience slower convergence. They rely on protocols like STP to prevent loops, but STP can take a significant amount of time (30–50 seconds) to recalculate and adapt to changes in the network, leading to delays in network recovery.

Option D: Limited to 4094 VLANs per switch.

While it is true that the VLAN range in Layer 2 networks is limited to 4094 due to the 12-bit VLAN identifier, this is not typically considered a limitation of Layer 2 switches in practice. This limitation is more of a design choice and does not necessarily hinder normal network operation for most users, as this range is large enough for most enterprise needs.

Option E: Increased flooding.

This is a limitation of Layer 2 switches. If a switch doesn't know the destination MAC address for a particular frame, it will flood the frame to all other ports. This can lead to unnecessary traffic in the network, especially if the MAC address table is not updated correctly or if the network topology causes frequent broadcast storms. Layer 2 switches have limited intelligence and are more prone to flooding compared to Layer 3 devices like routers.

The three main limitations of a traditional Layer 2 switch are:

B. Requires Layer 2 loop prevention
C. Slow response to topology changes
E. Increased flooding

These limitations stem from the inherent nature of Layer 2 switching and the protocols used to manage traffic at this layer.

Question No 4:

Which of the following statements about the VC-ID is false?

A. The vc-id is signaled in the control plane.
B. The vc-id is part of the data plane encapsulation.
C. There is a vc-id to vc-label mapping.
D. The vc-id has point to point significance.

Correct Answer: A

Explanation:

The VC-ID (Virtual Circuit Identifier) is an important concept in technologies like Multiprotocol Label Switching (MPLS), specifically in relation to Virtual Private Networks (VPNs) and Virtual Circuits. It is used to identify a virtual circuit in various network technologies. Let's break down each statement to understand why A is false:

A. The vc-id is signaled in the control plane.
This statement is false. The VC-ID is not signaled in the control plane; instead, it is typically associated with the data plane in the context of MPLS or other Layer 2 VPN technologies. The control plane is responsible for establishing and managing routing and signaling, but the VC-ID itself is used in the data plane for the actual forwarding of traffic. It's part of the packet's header for identifying the virtual circuit, not involved in signaling or control-related processes.
B. The vc-id is part of the data plane encapsulation.
This statement is true. The VC-ID is indeed part of the data plane encapsulation, especially in technologies like MPLS and Frame Relay. It is used to identify the virtual circuit within the encapsulated data, allowing the data to be correctly forwarded across the network.
C. There is a vc-id to vc-label mapping.
This statement is true. In MPLS and similar network technologies, there is a VC-ID to VC-label mapping. The VC-label is a label used to forward the traffic, and the VC-ID maps to this label to ensure proper routing and forwarding of data across the network.
D. The vc-id has point to point significance.
This statement is true. The VC-ID has point-to-point significance, meaning it uniquely identifies a specific virtual circuit between two points in a network. It ensures that traffic is correctly associated with the correct virtual circuit across the network's endpoints.

The false statement is A, which incorrectly states that the VC-ID is signaled in the control plane. The VC-ID is primarily part of the data plane and used for identifying virtual circuits during data forwarding.

Question No 5:

Assuming TLDP and RSVP are both being used in an MPLS network core, which of the following statements is true?

A. TLDP is used to create the inner label, RSVP is used to create the outer label.
B. TLDP is used to create the outer label, RSVP is used to create the inner label.
C. TLDP and RSVP cannot be used in the same network since they both provide the same label.
D. When RSVP is used, TLDP must be disabled and static VC labels should be used.
E. TLDP and RSVP can be used to create either labels based on how they are configured.

Answer: B

Explanation:

In MPLS networks, TLDP (Targeted LDP) and RSVP (Resource Reservation Protocol) are both used for label distribution but in different contexts. The main purpose of both protocols is to set up label-switched paths (LSPs) in the network, but they function differently and in some cases, can be used in conjunction to optimize the network.

Here’s an explanation of each option:

A. TLDP is used to create the inner label, RSVP is used to create the outer label.
This statement is incorrect. Typically, RSVP is responsible for reserving resources and signaling paths for MPLS, and it generally provides the outer label in a hierarchical label stack. TLDP, which is used for label distribution, provides the inner label in most cases, especially when working with LDP-based forwarding.
B. TLDP is used to create the outer label, RSVP is used to create the inner label.
This statement is correct. In a typical MPLS network with both RSVP and TLDP:

RSVP is often used to create the outer label for establishing paths through the core network, including traffic engineering.
TLDP is then used to distribute the inner label for the LSP, typically for Layer 2 VPNs, and to handle label distribution for MPLS forwarding.

The outer label is often used for the core forwarding of traffic, while the inner label is used for finer granularity in routing, especially in VPNs.
C. TLDP and RSVP cannot be used in the same network since they both provide the same label.
This is incorrect. While both TLDP and RSVP are used for label distribution, they do not conflict with each other. RSVP typically provides the outer label in an MPLS stack, while TLDP provides the inner label. Therefore, they can coexist in a network, with each protocol serving its role.
D. When RSVP is used, TLDP must be disabled and static VC labels should be used.
This statement is incorrect. RSVP and TLDP can be used in the same network simultaneously for different purposes (as described in option B). Disabling TLDP or using static labels is unnecessary when RSVP is used for label distribution.
E. TLDP and RSVP can be used to create either labels based on how they are configured.
This is incorrect. While both protocols are used for label distribution, the typical role of RSVP is to create the outer label and manage traffic engineering, while TLDP creates the inner label, especially in the context of Layer 2 VPNs. The label assignment is generally not interchangeable between the two protocols.

In conclusion, the correct statement is B: TLDP is used to create the outer label, RSVP is used to create the inner label. This setup ensures that the labels are distributed properly for both core MPLS routing and edge services like VPNs.

Question No 6:

Fill in the blank for this next sentence. Flooded traffic received on any ____________ in the service is replicated to other spoke SDPs and SAPs and not transmitted on any mesh SDPs.

A. Spoke SDP
B. Mesh SDP
C. Either (a) or (b) will make this sentence true.
D. Neither (a) nor (b) will make this sentence true.

Answer: A

Explanation:

In the context of network services, particularly those involving MPLS (Multiprotocol Label Switching) or Ethernet services, the terms spoke SDP and mesh SDP refer to different types of Service Delivery Points (SDPs) used to manage traffic between different points in a service. Let's break down the options:

A. Spoke SDP: A spoke SDP is typically used in a hub-and-spoke topology where traffic coming into the spoke from a spoke or SAP (Service Access Point) is replicated to other spoke SDPs and SAPs. Importantly, flooded traffic from a spoke SDP is not sent to mesh SDPs, as the mesh SDPs are typically part of a different traffic distribution model used in a full mesh topology. Therefore, the sentence would be correct with "spoke SDP," as the flooded traffic should be sent only to other spoke SDPs and SAPs, avoiding transmission over mesh SDPs.
B. Mesh SDP: In contrast, a mesh SDP is part of a full mesh topology, where each node is directly connected to every other node in the network. Flooded traffic from a mesh SDP would typically be transmitted to other mesh SDPs, so this option does not align with the statement, as it would contradict the sentence's context of not transmitting the traffic on mesh SDPs.
C. Either (a) or (b) will make this sentence true: This is incorrect because, based on the sentence, only spoke SDP would work for correctly replicating flooded traffic to other spoke SDPs and SAPs, while mesh SDPs would not meet the described behavior.
D. Neither (a) nor (b) will make this sentence true: This option is incorrect because spoke SDP is the correct term to fill in the blank for the given context.

Therefore, the correct answer is A. Spoke SDP, as the flooded traffic received on a spoke SDP is indeed replicated to other spoke SDPs and SAPs and not transmitted on mesh SDPs.

Question No 7:

Port 1/1/1 has been configured as an access port with QinQ encapsulation. Which of the following three statements are true for ingress traffic assuming default configuration? (Choose 3)

A. sap 1/1/1:.0 is a valid sap id.
B. sap 1/1/1:100 will accept frames with a single tag of 100.
C. sap 1/1/1:200* will strip the top tag of 200 and the bottom tag will be transparently passed.
D. sap 1/1/1:0* will accept all untagged frames.
E. sap 1/1/1:0* will accept any tagged frames.

Answer: A, C, D

Explanation:

In a QinQ (802.1ad) encapsulation configuration, dual tagging is used, where an additional VLAN tag is inserted into the Ethernet frame. This allows service providers to carry traffic from multiple customers over the same network while maintaining customer VLAN separation. An access port with QinQ configured will handle ingress traffic with a specific behavior based on the Service Access Point (SAP) identifiers, which define how frames are handled for various VLANs.

Let's go through each option:

A. sap 1/1/1:*.0 is a valid sap id:
This is true. The *.0 syntax is valid for matching untagged frames. In QinQ, the *.0 is used as a wildcard to match frames without any tags, allowing the port to accept untagged frames. Hence, this is a valid SAP ID for ingress traffic.
B. sap 1/1/1:100 will accept frames with a single tag of 100*:
This is false. In QinQ encapsulation, the 100* SAP ID would match frames with two tags, where the outer tag matches 100, and the inner tag could be anything. However, this does not match frames with just a single VLAN tag. A single-tagged frame would not match this SAP ID.
C. sap 1/1/1:200 will strip the top tag of 200 and the bottom tag will be transparently passed*:
This is true. In a QinQ setup, when a frame matches a SAP ID with the format 200*, it means that the top (outer) tag will be stripped (removed), and the bottom (inner) tag will be passed transparently. This is how QinQ operates, where the inner tag is preserved while the outer tag is stripped for further processing.
D. sap 1/1/1:0 will accept all untagged frames*:
This is true. The 0* SAP ID is used to match untagged frames or frames with no VLAN tags. This wildcard matches all untagged frames and is typically used to handle frames that are not tagged or to accept any frames that come in without a VLAN tag.
E. sap 1/1/1:0 will accept any tagged frames*:
This is false. The 0* SAP ID specifically matches untagged frames, not tagged frames. Frames with any VLAN tags will not match this SAP ID, which is why it cannot accept tagged frames.

To summarize, the correct statements that are true for ingress traffic in a QinQ-configured access port are A, C, and D.

Question No 8:

Which of the following statements relating to VPLS is false?

A. A VPLS is a multipoint Layer 2 service.
B. A VPLS allows multiple customer sites to be connected in a single bridged domain.
C. A VPLS on a single node requires a SDP.
D. With an IP/MPLS infrastructure, service providers can provide multiple VPLS services over a common IP/MPLS infrastructure.
E. The VPLS switches traffic based on MAC address associated with the appropriate SAP.

Answer: C

Explanation:

Virtual Private LAN Service (VPLS) is a Layer 2 VPN technology used to connect geographically dispersed sites over an IP/MPLS backbone, providing a unified, transparent bridged network. Let's break down each statement to identify which one is false:

Option A: A VPLS is a multipoint Layer 2 service.
This statement is true. VPLS is a multipoint-to-multipoint service that allows multiple customer sites to be interconnected, operating at Layer 2 (Data Link layer), creating a virtual Ethernet LAN.
Option B: A VPLS allows multiple customer sites to be connected in a single bridged domain.
This statement is true. VPLS enables multiple customer sites to be part of a single bridged domain, where all sites behave as if they are part of the same Ethernet LAN, even if they are geographically distributed.
Option C: A VPLS on a single node requires a SDP.
This statement is false. VPLS services typically require a Service Distribution Point (SDP) in a multi-node setup to connect different customer sites. However, in the context of a single node, an SDP is not required. VPLS on a single node can be configured without an SDP because there is no need for the node to connect to other remote sites. This makes the requirement for an SDP unnecessary in a single-node VPLS configuration.
Option D: With an IP/MPLS infrastructure, service providers can provide multiple VPLS services over a common IP/MPLS infrastructure.
This statement is true. One of the key advantages of VPLS is its ability to allow multiple VPLS services to run over a single shared IP/MPLS network infrastructure, enabling providers to efficiently use resources while offering distinct Layer 2 VPN services to different customers.
Option E: The VPLS switches traffic based on MAC address associated with the appropriate SAP.
This statement is true. VPLS uses MAC addresses to switch traffic, and each customer site is typically associated with a specific Service Access Point (SAP), where the MAC addresses are used to forward Ethernet frames appropriately within the VPLS network.

In summary, Option C is false because a single-node VPLS does not require a Service Distribution Point (SDP). An SDP is necessary for interconnecting multiple nodes in a VPLS service, but for a standalone node, it is not required.

Question No 9:

Assume the port on CE-A is sending two tags, a top tag of 100 and a bottom tag of 500. PE-A is configured with a SAP id of 1/1/1:100.*.

How should PE-B be configured if CE-B is expecting a top tag of 200 and a bottom tag of 500?

A. PE-B will require a SAP id of "sap 1/1/1:500*".
B. PE-B will require a SAP id of "sap 1/1/1:100*".
C. PE-B will require a SAP id of "sap 1/1/1:500.200".
D. PE-B will require a SAP id of "sap 1/1/1:200*".

Answer: D

Explanation:

To understand the correct configuration of the SAP id on PE-B, let's break down the scenario step by step:

CE-A is sending two tags: a top tag of 100 and a bottom tag of 500.
PE-A is configured with a SAP id of 1/1/1:100*, which means it is receiving traffic with a top tag of 100 (the first tag) and is willing to accept any bottom tag (indicated by the *).
CE-B is expecting a top tag of 200 and a bottom tag of 500. This means PE-B must be configured to receive traffic with a top tag of 200 and any bottom tag of 500.

Let’s analyze each option:

A. PE-B will require a SAP id of "sap 1/1/1:500"* – This configuration is incorrect because the top tag of 200 is expected by CE-B, but this SAP id specifies a bottom tag of 500 and no top tag at all (which is not what we need).

B. PE-B will require a SAP id of "sap 1/1/1:100"* – This configuration is also incorrect because PE-B needs to receive a top tag of 200, not 100, which is the tag being sent by CE-A.

C. PE-B will require a SAP id of "sap 1/1/1:500.200" – This configuration is incorrect because the top tag should be 200, but the SAP id here has it reversed (with 500 being the top tag and 200 as the bottom tag). This does not match the required configuration.

D. PE-B will require a SAP id of "sap 1/1/1:200"* – This configuration is correct. The SAP id specifies a top tag of 200, which matches what CE-B is expecting. The * symbol indicates that any bottom tag can be accepted, but the important point is that PE-B needs to accept a top tag of 200, which this configuration does.

In conclusion, PE-B should be configured with the SAP id "sap 1/1/1:200"* to ensure that it matches the expected top tag of 200 while accepting any bottom tag. Therefore, the correct answer is D.

Question No 10:

Which of the following statements is false?

A. VPLS is a bridged LAN service.
B. VPLS provides L2 VPN services to CEs.
C. VPLS is a point-to-point service where CEs are presented with point-to-point virtual circuits.
D. CEs that are members of the same VPLS service instance communicate with each other as if they are connected via a bridged LAN.

Correct answer: C

Explanation:

To understand why option C is the false statement, we must first understand what VPLS (Virtual Private LAN Service) is and how it works.

A. VPLS is a bridged LAN service:
This statement is true. VPLS is indeed a bridged LAN service that allows multiple customer sites to be interconnected over a wide area network (WAN), effectively creating a virtual LAN (VLAN) across geographically dispersed locations. It uses MPLS (Multiprotocol Label Switching) technology to create the virtual LAN, allowing customer equipment (CEs) to communicate as though they are on the same physical LAN.
B. VPLS provides L2 VPN services to CEs:
This statement is true. VPLS is a Layer 2 (L2) VPN service, which means it operates at the data link layer and allows customer edge devices (CEs) to communicate with each other over a virtualized LAN. It provides the capability to connect remote sites as if they were on the same local network.
C. VPLS is a point-to-point service where CEs are presented with point-to-point virtual circuits:
This statement is false. VPLS is not a point-to-point service but a multipoint-to-multipoint service. This means that instead of creating point-to-point virtual circuits between customer sites, VPLS allows multiple customer sites (CEs) to be interconnected in a full mesh topology, where all CEs in the same VPLS instance can communicate with each other as if they are connected in a single bridged LAN. This creates a multipoint virtual network, not a series of point-to-point connections.
D. CEs that are members of the same VPLS service instance communicate with each other as if they are connected via a bridged LAN:
This statement is true. In VPLS, customer sites (CEs) that are part of the same VPLS service instance behave as if they are directly connected via a LAN, even though they are geographically dispersed. The service provides transparent bridging across the sites, making the communication between CEs appear as if they are on the same local network.

In conclusion, the false statement is C, because VPLS is a multipoint-to-multipoint service, not a point-to-point service.