Nokia 4A0-116 Practice Test Questions, Exam Dumps

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4A0-116 Nokia Practice Test Questions and Exam Dumps

Question No 1:

Which of the following statements about Multi-Protocol Label Switching networks is FALSE?

A. MPLS uses a signaling protocol to exchange labels between routers.
B. An LSR forwards data based on the MPLS labels.
C. An LSP is a bi-directional tunnel that uses MPLS labels to forward data.
D. The data is transparently carried from end to end.

Answer: C

Explanation:

Let's go through each option to determine which one is false:

A (MPLS uses a signaling protocol to exchange labels between routers): This is true. MPLS uses signaling protocols like Label Distribution Protocol (LDP) or Resource Reservation Protocol-Traffic Engineering (RSVP-TE) to exchange labels between routers. These protocols are responsible for distributing labels and setting up label-switched paths (LSPs) across the network.
B (An LSR forwards data based on the MPLS labels): This is true. Label Switching Routers (LSRs) are the core devices in an MPLS network. LSRs forward packets based on the MPLS labels attached to them, rather than by looking at the traditional Layer 3 IP header. This allows faster packet forwarding because the router only needs to look at the label rather than performing a full Layer 3 lookup.
C (An LSP is a bi-directional tunnel that uses MPLS labels to forward data): This is false. While Label Switched Paths (LSPs) are used in MPLS networks to forward packets, they are unidirectional by default. Each LSP carries traffic in one direction. If bi-directional traffic is needed, two separate LSPs are typically created—one for each direction. The idea of an LSP being a bi-directional tunnel is a misunderstanding of how LSPs work in MPLS.
D (The data is transparently carried from end to end): This is true. MPLS networks can carry traffic transparently between the source and the destination. The MPLS labels are added to packets and are used for routing purposes within the MPLS network. However, from the perspective of the end-user, the data is carried end-to-end without modification or disruption to the application traffic.

Conclusion: The false statement is C, as LSPs are unidirectional and not bi-directional by default in MPLS networks. Therefore, C is the correct answer.

Question No 2:

Which of the following statements about a Segment Routing SID is FALSE?

A. A Node-SID is usually associated with a router's system interface.
B. Adjacency-SID values are taken from the SRGB configured for the routing protocol.
C. A Prefix-SID can be configured directly as a label value or indirectly as an index.
D. An Adjacency-SID does not have to be configured.

Answer: B

Explanation:

Segment Routing (SR) utilizes different types of Segment Identifiers (SIDs) to direct the flow of traffic within a network. These include Node-SIDs, Prefix-SIDs, and Adjacency-SIDs, each serving a specific purpose.

Node-SID: This SID type is associated with a node (router) in the network. It often corresponds to the router's system interface, which means it is tied to the router itself. When a Node-SID is referenced, it implies routing traffic toward a specific router within the network.

Prefix-SID: A Prefix-SID represents a specific IP prefix, typically associated with a network or subnet. This SID can be configured either directly, where it is treated as a label value, or indirectly through an index that references an entry in a local or global table.

Adjacency-SID: This SID is related to a particular link or adjacency between two nodes in the network. An Adjacency-SID can be configured in the network, although it is not always required. It is used when specific traffic needs to follow a path through a particular link between two routers, bypassing other available paths.

SRGB (Segment Routing Global Block): This is a range of label values that is reserved for segment routing labels. It is configured on routers to define the range of labels that can be used for various SIDs, including Prefix-SIDs and Adjacency-SIDs.

The statement in Option B is FALSE because Adjacency-SID values are not directly taken from the SRGB configured for the routing protocol. Instead, they are typically selected from a separate, predefined range that can be configured independently of the SRGB. This differentiates them from Prefix-SIDs, which are often associated with the SRGB.

Thus, Option B is the false statement because it incorrectly implies that Adjacency-SIDs are taken from the SRGB, when in fact, they are typically assigned from a different segment range.

Question No 3:

Which of the following statements about Segment Routing is FALSE?

A. No path signaling is required to establish an SR tunnel.
B. Intermediate routers do not maintain any tunnel information.
C. A link-state IGP is required to distribute SID information.
D. For TE-constrained tunnels, each data packet typically carries a single MPLS label to specify the tunnel path.

Answer: D

Explanation:

Segment Routing (SR) is a method of forwarding packets through an MPLS network that uses segments to determine paths rather than traditional signaling protocols like LDP or RSVP-TE. The key benefit of SR is that it simplifies the network by removing the need for state information to be maintained at each router. Each of the options explores a key aspect of Segment Routing.

A. "No path signaling is required to establish an SR tunnel" is true. One of the primary features of Segment Routing is that it removes the need for path signaling. In traditional MPLS, signaling protocols such as RSVP-TE or LDP are required to establish a label-switched path (LSP). With SR, the path is determined by the source node, which encodes the path in the packet header as a list of segments. This eliminates the need for complex signaling between routers to set up paths.

B. "Intermediate routers do not maintain any tunnel information" is true. Segment Routing's design ensures that intermediate routers do not need to maintain any state information about the path or tunnel. This simplifies the network and reduces the overhead involved in maintaining and updating path state, as each packet carries all the necessary information in the form of a segment list.

C. "A link-state IGP is required to distribute SID information" is true. In Segment Routing, the Segment Identifier (SID) is distributed using an Interior Gateway Protocol (IGP) like OSPF or IS-IS. These link-state protocols are responsible for sharing the segment information across the network, ensuring that each router knows the SIDs and how to forward traffic.

D. "For TE-constrained tunnels, each data packet typically carries a single MPLS label to specify the tunnel path" is false. For traffic engineering (TE)-constrained tunnels in Segment Routing, the data packets typically carry multiple MPLS labels, not just a single label. Each label corresponds to a specific segment, and the packet traverses the network based on the sequence of labels (segment list) in the packet header. This allows for more flexibility in path selection and the ability to consider various constraints like bandwidth, latency, or topology when selecting the path. Therefore, this statement is false.

Segment Routing simplifies network operations by reducing the complexity of state maintenance and signaling while still allowing for traffic engineering and path control. However, it relies on a specific approach to forwarding traffic using segment lists and may involve multiple labels for TE-constrained tunnels.

Question No 4:

Which of the following statements about a Segment Routing SID is FALSE?

A. A local Node-SID can be configured directly as an MPLS label.
B. A router advertises its local Node-SID as a local SRGB and an index only if it is configured as an index.
C. All routers do NOT need to have the same SRGB range configured.
D. A local Node-SID can be configured as an index.

Answer: B

Explanation:

Segment Routing (SR) is a modern and flexible way to implement source routing, where a source node specifies a list of segments (routing instructions) that are followed by the packets. Segment Routing uses Segment Identifiers (SIDs) that are associated with specific actions in the network. The Node-SID is a unique identifier for a node, and it can be used for packet forwarding in various segment routing techniques.

Now, let’s go over each option to explain why B is the correct choice:

A. A local Node-SID can be configured directly as an MPLS label.
This statement is true. A local Node-SID, which represents the identity of a router in a Segment Routing architecture, can indeed be configured directly as an MPLS label. In Segment Routing, the SID can be mapped directly to an MPLS label, allowing it to be used in MPLS forwarding for network traffic.
B. A router advertises its local Node-SID as a local SRGB and an index only if it is configured as an index.
This is the false statement. In Segment Routing, a router advertises its local Node-SID in the Segment Routing Global Block (SRGB) regardless of whether it is configured as an index or not. The advertisement of the Node-SID does not depend on whether the router is configured with an index or not. The SRGB is used to allocate SIDs for segment routing, and Node-SIDs are a part of that allocation process. The router advertises the SID as part of its SRGB to allow other routers to know the SID associated with it.
C. All routers do NOT need to have the same SRGB range configured.
This statement is true. It is not mandatory for all routers to use the same Segment Routing Global Block (SRGB) range. While having the same SRGB range simplifies network design and configuration, Segment Routing allows for flexibility. Different routers in the network can use different SRGB ranges for their Node-SIDs as long as they maintain consistency within their own configuration and segment routing architecture.
D. A local Node-SID can be configured as an index.
This statement is true. A local Node-SID can be configured as an index within the Segment Routing Global Block (SRGB). This means that the Node-SID can be referenced by an index number, which helps in simplifying and organizing the allocation of SIDs for nodes in a network.

In conclusion, the false statement is B, as the advertisement of a Node-SID as part of the SRGB does not depend on whether the router is configured with an index.

Question No 5:

When OSPF is used to support Segment Routing, the first byte of the link-state ID associated with each of the opaque LSAs indicates the type of information being advertised.

Which of the following associations between the first-byte value and its meaning is FALSE?

A. Value 1 - Traffic Engineering
B. Value 4 - Router Info
C. Value 7 - SRGB Range
D. Value 8 - Extended Link Info

Answer: C

Explanation:

In OSPF, when it is used to support Segment Routing (SR), the first byte of the link-state ID within opaque LSAs (Link State Advertisements) is critical in determining the type of information being advertised. The values associated with each type indicate different types of data relevant to Segment Routing functionalities. Each value is used to describe specific routing or segment information, crucial for the operation of SR.

Option A: Value 1 - Traffic Engineering
The first byte value of 1 corresponds to Traffic Engineering information. This value is used for OSPF advertisements that carry traffic engineering data. This is true, as Traffic Engineering is a key part of Segment Routing, helping routers determine how to allocate and manage resources efficiently across the network.

Option B: Value 4 - Router Info
The first byte value of 4 corresponds to Router Information. This association is also correct. When advertising router information, the opaque LSA carries details about the router itself, which is essential for network-wide routing decisions and optimizations in SR-enabled networks.

Option C: Value 7 - SRGB Range
The value of 7 is not associated with SRGB Range. In fact, SRGB (Segment Routing Global Block) Range information is associated with the value of 3, not 7. This means that Option C is the incorrect association. The SRGB Range indicates the range of segment IDs that can be used for Segment Routing and is crucial for the configuration of Segment Routing within the network.

Option D: Value 8 - Extended Link Info
The first byte value of 8 corresponds to Extended Link Information. This is correct. Extended Link Information is used to advertise additional link attributes, which can be vital for advanced network features in OSPF, including those needed for Segment Routing.

Thus, the false association is in Option C, where the first byte value of 7 is incorrectly stated as associated with SRGB Range. The correct value for SRGB Range is 3.

Question No 6:

Which of the following steps is NOT required when configuring IS-IS to support Segment Routing?

A. MPLS label range reserved for Segment Routing.
B. Enable interfaces used for Segment Routing under the MPLS context.
C. The flooding scope of Segment Routing information.
D. The Segment Routing Global Block range.

Answer: C

Explanation:

When configuring IS-IS to support Segment Routing, certain steps are necessary for its proper operation. Segment Routing (SR) leverages a new way to route traffic using "segments" instead of traditional path-based routing, and IS-IS must be configured correctly to support these segments.

A. MPLS label range reserved for Segment Routing – This step is critical for Segment Routing configuration. Segment Routing uses labels from a specific MPLS label range to define the segments. Without reserving an MPLS label range for Segment Routing, the network would not have the appropriate label space to use for forwarding packets based on the segments defined by the SR configuration.

B. Enable interfaces used for Segment Routing under the MPLS context – This is also an essential step. For IS-IS to support Segment Routing, interfaces need to be enabled for MPLS so that the network devices can process the segment labels associated with SR. Enabling these interfaces ensures that Segment Routing information can be advertised and processed correctly across the network.

C. The flooding scope of Segment Routing information – The flooding scope refers to how the Segment Routing information is distributed within the IS-IS protocol. In Segment Routing, this is typically done by flooding the information across the network, ensuring that all routers can access the segment information. However, this specific step of defining the flooding scope is not strictly necessary for enabling Segment Routing itself; it is more about optimizing how SR information is propagated. Therefore, this step is not mandatory for basic SR configuration.

D. The Segment Routing Global Block range – Defining the Segment Routing Global Block (SRGB) is required in the configuration. The SRGB determines the range of labels that are used globally across the Segment Routing-enabled network. Without defining the SRGB, there would be no clear space from which to allocate segment IDs, so this is a crucial step in the configuration.

Thus, while the other steps directly affect the operation of IS-IS with Segment Routing, defining the flooding scope of Segment Routing information (option C) is not absolutely required when configuring Segment Routing.

Question No 7:

What type of advertisement in OSPF type-10 Opaque LSAs carries a router's local SRGB information?

A. Extended Prefix Info
B. Router Info
C. Extended Link Info
D. Traffic Engineering Info

Answer: B

Explanation:

OSPF (Open Shortest Path First) type-10 Opaque LSAs (Link-State Advertisements) are used to convey information that is not included in traditional OSPF LSAs. They allow OSPF to carry additional types of information that can be used by various OSPF extensions, especially for supporting newer features. One of the key uses of Opaque LSAs is to carry information related to Segment Routing (SR), and the SRGB (Segment Routing Global Block) is one of the critical pieces of information used in Segment Routing.

In this case, Router Info advertisements in OSPF type-10 Opaque LSAs are the ones that carry the local SRGB (Segment Routing Global Block) information. The SRGB is a range of labels used by routers for segment routing, and each router typically has its own local SRGB for managing labels for the SR.

Here’s a breakdown of the options:

A. Extended Prefix Info: This option refers to OSPF LSAs that convey additional prefix information, but it is not related to carrying SRGB information. Instead, it is concerned with advertising extended prefix data.
B. Router Info: Correct. This advertisement type in OSPF type-10 Opaque LSAs is used to carry a router's local SRGB information, which helps in label assignment for segment routing.
C. Extended Link Info: This option pertains to additional link state information in OSPF but is not specifically used for SRGB information.
D. Traffic Engineering Info: This type of information is typically carried in OSPF TE extensions, specifically OSPF type-9 LSAs, but it is not used to carry SRGB information directly.

Therefore, Router Info (B) is the correct answer, as it specifically carries the local SRGB information for routers in an OSPF network using Segment Routing.

Question No 8:

Which of the following is not required to be advertised by a router participating in Segment Routing?

A. Local Node-SID
B. Adjacency-SIDs
C. Support for SR-MPLS for IPv4 or IPv6, or SRv6
D. SRGB when SRv6 is configured

Answer: C

Explanation:

Segment Routing (SR) is an advanced routing paradigm that allows a router to forward packets based on an explicit path defined by a series of segments. Segment Routing utilizes a technique where the path is encoded as a sequence of segments. The segments can be represented in several formats, like MPLS (SR-MPLS) for IPv4 or IPv6, or SRv6, which uses IPv6 for the encoding of segments.

The key concept behind Segment Routing is to advertise specific information to enable routers to properly process and forward the packets according to the segment identifiers (SIDs). Here’s a breakdown of the choices provided:

A. Local Node-SID: The Local Node-SID is a segment identifier (SID) that uniquely identifies a router within a network. This is required to be advertised because it helps in identifying the router for routing decisions.
B. Adjacency-SIDs: These are SIDs that represent a specific link between two nodes. These SIDs are important for enabling fine-grained traffic engineering and must also be advertised to inform routers of the available links for traffic forwarding.
C. Support for SR-MPLS for IPv4 or IPv6, or SRv6: This refers to the type of Segment Routing (SR-MPLS or SRv6) that the router supports. While it is important to configure a router to support one or the other, the support itself does not need to be advertised as part of the SR protocol. Routers may simply advertise the segments (like Node-SIDs, Adjacency-SIDs, etc.) that they can handle, without necessarily advertising their support for the protocol.
D. SRGB when SRv6 is configured: The Segment Routing Global Block (SRGB) is a range of segment IDs that a router uses when participating in SR-MPLS or SRv6. This needs to be advertised so that routers within the network can understand the range of segment IDs the router is using.

Thus, support for SR-MPLS for IPv4 or IPv6, or SRv6 (option C) is not directly required to be advertised by a router participating in Segment Routing. What needs to be advertised are the actual segments (Node-SIDs, Adjacency-SIDs, etc.), while the support for a specific protocol (SR-MPLS or SRv6) is more of a configuration aspect.

Question No 9:

Which of the following statements about Segment Routing tunnels is FALSE?

A A Segment Routing tunnel defined by a Node-SID uses the shortest IGP Path.
B A Segment Routing tunnel can be defined by multiple Node-SIDs.
C A Segment Routing tunnel can be defined by a combination of Node-SIDs and Adjacency-SIDs.
D For a Segment Routing tunnel, an intermediate router will always forward the packet based on the best IGP path.

Answer: D

Explanation:

Segment Routing (SR) is a modern and efficient routing technique that leverages the concept of segments and can simplify network operations by encoding forwarding instructions directly within the packet headers. Each packet in an SR domain is associated with a list of segments, and these segments can be Node-SIDs or Adjacency-SIDs.

Option A, which states that a Segment Routing tunnel defined by a Node-SID uses the shortest IGP path, is true. When a Node-SID is used in Segment Routing, the path to the node associated with the SID is typically determined by the IGP (Interior Gateway Protocol) such as OSPF or IS-IS, and it generally represents the shortest path to that node.

Option B, which claims that a Segment Routing tunnel can be defined by multiple Node-SIDs, is also true. A Segment Routing tunnel can involve multiple Node-SIDs, each of which represents a hop to a specific router or node within the network. The path taken can involve multiple such hops to traverse the network according to the segment list.

Option C is also true. A Segment Routing tunnel can be defined by a combination of Node-SIDs and Adjacency-SIDs. An Adjacency-SID refers to a specific link between two nodes, and using both types of SIDs in a combination allows more granular control over the forwarding behavior of packets within the SR domain.

Option D is false. For a Segment Routing tunnel, the intermediate router does not always forward the packet based on the best IGP path. Instead, the forwarding decision is based on the Segment List embedded in the packet header, which dictates the specific path the packet should take. The intermediate routers simply process the segment list and forward the packet according to the segments, regardless of the best IGP path. This means that the best IGP path may not necessarily be used in the forwarding process, as the path is determined by the segment list and the instructions encoded in the packet.

In conclusion, option D is the incorrect statement, as the forwarding decision in Segment Routing is determined by the segment list rather than the IGP's best path.

Question No 10:

Which of the following is NOT one of the main goals of traffic engineering?

A. Utilizing redundant links.
B. Avoiding potential congestion points in the network.
C. Defining traffic paths based on various constraints.
D. Using the shortest possible path through the network to the destination.

Answer: D

Explanation:

Traffic engineering is the process of optimizing the flow of data across a network to ensure efficient, reliable, and secure communication. It involves several key goals aimed at maintaining optimal network performance and minimizing issues such as congestion and inefficiency.

A. Utilizing redundant links is a common goal in traffic engineering. Redundant links are used to provide backup routes for traffic in case of network failures. This enhances network reliability and resilience by ensuring that there is an alternative route available if one path becomes unavailable.

B. Avoiding potential congestion points in the network is another important goal of traffic engineering. Identifying and preventing congestion is crucial for maintaining network efficiency. Engineers monitor network traffic to detect potential bottlenecks and adjust routing or traffic distribution to avoid these congestion points.

C. Defining traffic paths based on various constraints is also a key objective in traffic engineering. Networks may have multiple constraints such as bandwidth limitations, latency requirements, and quality of service needs. Traffic engineering aims to define paths for data to traverse the network that meet these constraints while avoiding performance degradation.

D. Using the shortest possible path through the network to the destination, while seemingly intuitive, is not typically a primary goal of traffic engineering. In fact, traffic engineering often moves away from using the shortest path when it does not optimize the overall network performance. Shortest path routing can sometimes lead to congestion in certain areas of the network, as it may not take into account factors like network capacity, load balancing, or reliability. Instead, traffic engineering focuses on finding paths that distribute traffic efficiently across the network, even if these paths are not the shortest in terms of hops or distance.