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Question 361

Which protocol is commonly used by service providers to distribute MPLS labels for IGP-learned prefixes?

1. LDP
2. BGP
3. SNMP
4. NTP

Correct Answer: 1

Explanation

Label Distribution Protocol (LDP) is commonly used to distribute MPLS labels for routes learned through an Interior Gateway Protocol such as OSPF or IS-IS. LDP establishes sessions between neighboring Label Switching Routers and distributes label bindings associated with Forwarding Equivalence Classes. These bindings allow routers to build Label Switched Paths through the MPLS network. BGP can also distribute VPN and labeled routing information in specific architectures, but its primary role differs from traditional LDP label distribution. SNMP is used for management, while NTP synchronizes clocks. Therefore, LDP is correct.

Question 362

Which MPLS protocol establishes a targeted session with a non-directly connected LDP neighbor?

1. RSVP
2. Targeted LDP
3. BFD
4. OSPF

Correct Answer: 2

Explanation

Targeted LDP allows an LDP session to be established between routers that are not directly connected at the IP layer. Unlike normal LDP discovery, which uses link-local or directly connected discovery mechanisms, targeted LDP uses targeted Hello messages toward a specific remote LDP peer. This capability is useful in certain MPLS VPN, pseudowire, and service-provider designs where label information must be exchanged across non-directly connected routers. RSVP is used for traffic engineering, BFD provides fast failure detection, and OSPF is an IGP. Therefore, Targeted LDP is correct.

Question 363

Which protocol is commonly used to signal traffic-engineered MPLS tunnels with explicit resource information?

1. LDP
2. RSVP-TE
3. SNMP
4. DHCP

Correct Answer: 2

Explanation

RSVP-TE is a signaling protocol used for MPLS Traffic Engineering. It can establish explicitly routed Label Switched Paths and carry information related to bandwidth and other traffic-engineering constraints. This allows network operators to influence the path taken by traffic instead of relying solely on the shortest IGP path. LDP normally follows the IGP topology rather than calculating resource-constrained explicit paths. SNMP is a management protocol, while DHCP provides host configuration services. Therefore, RSVP-TE is the correct protocol for signaling traffic-engineered MPLS tunnels.

Question 364

Which Segment Routing mechanism can provide local protection around a failed link or node without requiring a separately signaled backup tunnel?

1. TI-LFA
2. MED
3. VRRP
4. DHCP Relay

Correct Answer: 1

Explanation

Topology Independent Loop-Free Alternate (TI-LFA) provides fast local protection in Segment Routing networks. When a link or node failure occurs, the protecting router can use a precomputed Segment Routing repair path to steer traffic around the failure. TI-LFA does not require a separately signaled RSVP-TE backup tunnel for each protected path. It can therefore provide rapid local repair while using the existing Segment Routing control-plane information. MED is a BGP attribute, VRRP provides gateway redundancy, and DHCP Relay forwards DHCP messages. Therefore, TI-LFA is correct.

Question 365

What is the primary purpose of an SR Policy?

1. Define a desired path or set of constraints for traffic
2. Assign IPv4 addresses to subscribers
3. Authenticate BGP neighbors
4. Synchronize network clocks

Correct Answer: 1

Explanation

An SR Policy defines how traffic should be steered through a Segment Routing network. It can contain candidate paths and segment lists that represent desired forwarding behavior. Policies can be used for traffic engineering, service-based steering, and path selection based on constraints such as topology, latency, or administrative requirements. SR Policies operate within the Segment Routing architecture and can use SIDs to encode forwarding instructions. IP address assignment, BGP authentication, and clock synchronization are separate functions. Therefore, defining a desired traffic path is the correct answer.

Question 366

Which Segment Routing concept allows traffic to be steered toward a specific policy using a single segment identifier?

1. Binding SID
2. Node-SID
3. Anycast address
4. Route Target

Correct Answer: 1

Explanation

A Binding SID represents an SR Policy as a segment identifier. When a packet is steered using a Binding SID, the network can associate that SID with the corresponding policy and apply the policy’s segment list or candidate path. This provides a compact way to reference complex forwarding behavior. A Node-SID normally represents reachability toward a node, while Route Targets control VPN route import and export. Anycast addresses can represent multiple devices but are not the specific mechanism described here. Therefore, Binding SID is correct.

Question 367

Which SR-MPLS SID type can represent multiple routers that provide the same anycast service or function?

1. Anycast-SID
2. Adjacency-SID
3. VPN-SID
4. Route-SID

Correct Answer: 1

Explanation

An Anycast-SID can represent a set of routers that share a common anycast function or prefix. Traffic directed toward the Anycast-SID is forwarded toward the nearest suitable member according to the Segment Routing topology and forwarding rules. This can be useful for redundant services, distributed functions, or multiple equivalent service nodes. An Adjacency-SID identifies a particular adjacency, while VPN-SID and Route-SID are not standard generic SR-MPLS SID categories. Therefore, Anycast-SID is correct.

Question 368

In SRv6, what does a locator primarily identify?

1. The network location or block associated with an SRv6 node
2. An MPLS VPN Route Target
3. A BGP community
4. An Ethernet VLAN

Correct Answer: 1

Explanation

In SRv6, a locator identifies the routing location or address block associated with an SRv6 node. It forms an important part of an SRv6 Segment Identifier (SID) structure and allows the network to route the packet toward the appropriate SRv6 node. Additional portions of the SID can represent functions and arguments depending on the SRv6 design. Route Targets belong to MPLS VPN policy, BGP communities carry routing policy information, and VLANs identify Ethernet broadcast domains. Therefore, identifying the SRv6 node’s network location is correct.

Question 369

Which IPv6 mechanism automatically provides hosts with network prefixes and default-router information without requiring DHCPv6 for those basic functions?

1. Router Advertisement
2. BGP UPDATE
3. ARP
4. LDP

Correct Answer: 1

Explanation

IPv6 Router Advertisement (RA) messages are sent by routers as part of Neighbor Discovery. They can provide hosts with information such as network prefixes, default-router information, address-configuration flags, and other parameters. Stateless Address Autoconfiguration can use the advertised prefix to generate addresses without requiring a DHCPv6 server for the basic address-configuration process. BGP UPDATE is used for routing, ARP is replaced by IPv6 Neighbor Discovery, and LDP distributes MPLS labels. Therefore, Router Advertisement is correct.

Question 370

Which IPv6 protocol can provide stateful address assignment and additional configuration information to hosts?

1. DHCPv6
2. LACP
3. PIM
4. RSVP-TE

Correct Answer: 1

Explanation

DHCPv6 can provide stateful IPv6 address assignment and additional configuration information to hosts. Depending on the network design, Router Advertisements can indicate whether hosts should use DHCPv6 for address configuration or other parameters. DHCPv6 can also provide information such as DNS server configuration. LACP manages link aggregation, PIM supports multicast routing, and RSVP-TE is used for traffic engineering. Therefore, DHCPv6 is the correct protocol for stateful IPv6 address assignment and related configuration.

Question 371

Which IPv6 Neighbor Discovery message is normally sent by a host to discover routers on its local link?

1. Router Solicitation
2. Router Advertisement
3. Neighbor Advertisement
4. Echo Reply

Correct Answer: 1

Explanation

An IPv6 host can send a Router Solicitation (RS) message to request Router Advertisements from routers on the local link. The router responds with an RA containing information such as network prefixes, default-router information, and configuration flags. Router Advertisements can also be sent periodically without an RS. Neighbor Solicitation and Neighbor Advertisement are primarily used for neighbor resolution, Duplicate Address Detection, and related Neighbor Discovery operations. ICMPv6 Echo Reply is associated with ping responses. Therefore, Router Solicitation is correct.

Question 372

Which multicast protocol feature allows a receiver to explicitly request specific multicast sources?

1. IGMPv1
2. IGMPv2
3. IGMPv3
4. PIM-DM

Correct Answer: 3

Explanation

IGMPv3 supports Source-Specific Multicast (SSM) receiver signaling by allowing hosts to specify the multicast sources from which they want to receive traffic. This provides source filtering capabilities that are not available in the same form with earlier IGMP versions. IGMPv1 provides basic membership reporting, while IGMPv2 adds features such as explicit leave messages. PIM-DM is a multicast routing protocol rather than a host membership protocol. Therefore, IGMPv3 is the correct answer for explicit source selection.

Question 373

Which multicast routing protocol is commonly used with Source-Specific Multicast?

1. PIM-SSM
2. BGP
3. OSPF
4. LDP

Correct Answer: 1

Explanation

PIM-SSM is specifically designed for Source-Specific Multicast operation. In SSM, receivers identify both the multicast group and the desired source, allowing the network to build multicast forwarding trees directly from the source to interested receivers. This eliminates the need for a traditional shared Rendezvous Point in the basic SSM model. BGP and OSPF are primarily unicast routing protocols, while LDP is used for MPLS label distribution. Therefore, PIM-SSM is correct.

Question 374

What is the main role of a Rendezvous Point in traditional PIM-SM operation?

1. Help establish the shared multicast distribution tree
2. Assign MPLS labels
3. Provide BGP authentication
4. Allocate IPv6 addresses

Correct Answer: 1

Explanation

In traditional PIM Sparse Mode, the Rendezvous Point (RP) provides a meeting point for multicast sources and receivers during the initial multicast distribution process. Receivers can join a shared tree rooted at the RP, while sources initially register their traffic with the RP. Depending on the network and configuration, routers may later switch to a source-specific shortest-path tree. The RP does not allocate MPLS labels, authenticate BGP sessions, or assign IPv6 addresses. Therefore, helping establish the shared multicast distribution tree is the correct answer.

Question 375

Which multicast mechanism can provide redundancy by using multiple RPs that share the same logical RP address?

1. Anycast-RP
2. LACP
3. BFD
4. VRF Lite

Correct Answer: 1

Explanation

Anycast-RP allows multiple physical RP routers to use the same logical RP address. This provides RP redundancy and can distribute multicast source registration and receiver traffic among multiple RP devices. In many designs, MSDP can be used between Anycast-RP routers to synchronize source information. LACP provides Ethernet link aggregation, BFD provides rapid failure detection, and VRF Lite provides routing-table separation without MPLS VPN transport. Therefore, Anycast-RP is the correct multicast redundancy mechanism.

Question 376

Which PIM mechanism helps determine the correct upstream interface toward a multicast source?

1. RPF check
2. DR election
3. Route Reflection
4. LSP Ping

Correct Answer: 1

Explanation

The Reverse Path Forwarding (RPF) check verifies that multicast traffic arrives through the interface the router considers to be the correct path toward the source. The router uses its unicast routing information to determine the RPF interface. If multicast traffic arrives on another interface, the packet can be rejected to prevent loops and incorrect forwarding. DR election has a different role in PIM, Route Reflection belongs to BGP, and LSP Ping is an MPLS OAM mechanism. Therefore, the RPF check is correct.

Question 377

Which QoS mechanism can randomly or probabilistically drop packets before a queue becomes completely full to manage congestion?

1. WRED
2. LLQ
3. Shaping
4. Marking

Correct Answer: 1

Explanation

Weighted Random Early Detection (WRED) is a congestion-avoidance mechanism that can begin dropping packets before a queue reaches its maximum capacity. It uses queue thresholds and packet characteristics such as precedence or DSCP to determine when and how aggressively packets should be dropped. This can help reduce the likelihood of synchronized TCP congestion and maintain queue availability. LLQ provides strict priority service, shaping controls traffic transmission rates through buffering, and marking changes packet classification values. Therefore, WRED is the correct answer.

Question 378

Which QoS function changes a packet’s DSCP value to apply a different forwarding treatment?

1. Classification
2. Marking
3. Policing
4. Queuing

Correct Answer: 2

Explanation

QoS marking changes a packet’s classification value, such as its DSCP field, so downstream devices can apply an appropriate Per-Hop Behavior. Classification determines which traffic class a packet belongs to, while marking modifies the value used to represent that classification. Policing controls traffic rates and may optionally remark packets, but marking itself refers specifically to setting classification information. Queuing determines how packets are scheduled for transmission. Therefore, marking is the correct answer.

Question 379

Which automation protocol commonly uses YANG data models to configure and retrieve structured network configuration?

1. NETCONF
2. FTP
3. SMTP
4. TFTP

Correct Answer: 1

Explanation

NETCONF is a network management protocol designed to configure and retrieve structured device information. It commonly uses YANG data models to define the structure and semantics of configuration and operational data. NETCONF supports capabilities such as candidate configuration, validation, and controlled commits on devices that implement those features. FTP, SMTP, and TFTP are general-purpose protocols that do not provide the same model-driven network configuration framework. Therefore, NETCONF is the correct answer.

Question 380

Which HTTP method is commonly used by RESTCONF to completely replace the configuration represented by a target resource?

1. PATCH
2. POST
3. PUT
4. GET

Correct Answer: 3

Explanation

RESTCONF commonly uses the HTTP PUT method to replace the configuration represented by a target resource. PUT is generally associated with creating or completely replacing a resource at a known URI. PATCH is used for partial modifications, POST is commonly used to create subordinate resources or invoke operations depending on the API, and GET retrieves data without modifying it. RESTCONF uses YANG data models and HTTP-based operations to provide programmatic access to network configuration and operational data. Therefore, PUT is the correct answer.