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Question 241

Which QoS field is commonly used to classify IP packets into different service classes?

1. MPLS Label
2. DSCP
3. TCP Window
4. VLAN ID

Correct Answer: 2

Explanation

Differentiated Services Code Point (DSCP) is a field in the IP header used to classify packets according to their required forwarding treatment. Service providers can use DSCP values to identify traffic classes such as voice, video, critical applications, or best-effort traffic. Once packets are classified, QoS policies can apply appropriate queuing, scheduling, policing, or marking actions. The MPLS label identifies an MPLS forwarding context, TCP Window controls flow characteristics, and VLAN ID identifies an Ethernet VLAN. Therefore, DSCP is the correct field for IP traffic classification.

Question 242

Which MPLS header field is commonly used to carry QoS-related traffic-class information?

1. Label
2. TTL
3. Traffic Class
4. BoS

Correct Answer: 3

Explanation

The MPLS Traffic Class (TC) field carries information that can be used for QoS classification and treatment of MPLS packets. It contains three bits and is commonly associated with differentiated service behavior within MPLS networks. Providers can use the TC value to map packets into appropriate queues or forwarding classes. The Label field identifies the forwarding context, the TTL field helps prevent packets from circulating indefinitely, and the Bottom of Stack bit indicates whether the label is the final label in the stack. Therefore, Traffic Class is correct.

Question 243

Which QoS mechanism can selectively discard packets before a queue becomes completely full to reduce the impact of congestion?

1. WRED
2. LLQ
3. CBWFQ
4. LACP

Correct Answer: 1

Explanation

Weighted Random Early Detection (WRED) is a congestion-avoidance mechanism that can begin dropping packets before a queue reaches full capacity. By using thresholds and packet classifications, WRED can reduce the likelihood of severe congestion and tail drops. It can also provide different treatment based on packet markings or precedence values. LLQ provides strict priority scheduling, CBWFQ allocates bandwidth among traffic classes, and LACP manages link aggregation. Therefore, WRED is the correct mechanism for early and selective packet dropping during congestion.

Question 244

Which QoS process changes a packet’s DSCP value so that downstream devices can recognize its traffic class?

1. Shaping
2. Marking
3. Policing
4. Scheduling

Correct Answer: 2

Explanation

QoS marking changes classification information in a packet, such as the DSCP value in an IP header. Marking allows downstream devices to recognize the intended traffic class and apply consistent forwarding treatment. For example, an edge router may classify application traffic and mark it before sending it into the service provider network. Shaping controls the transmission rate, policing enforces a traffic rate and can drop or remark excess traffic, and scheduling determines how queues receive service. Therefore, marking is the correct QoS process.

Question 245

Which MPLS Traffic Engineering mechanism can use a precomputed backup path to provide rapid protection after a link or node failure?

1. RSVP authentication
2. FRR
3. Route Refresh
4. ARP

Correct Answer: 2

Explanation

Fast Reroute (FRR) provides rapid protection for MPLS Traffic Engineering paths by allowing traffic to switch to a pre-established or precomputed backup path after a failure. This minimizes the time required to restore forwarding while the broader control plane converges. FRR can provide local protection against failures such as links or nodes depending on the protection method used. RSVP authentication does not provide traffic protection, Route Refresh is a BGP function, and ARP resolves IPv4 addresses to MAC addresses. Therefore, FRR is the correct MPLS protection mechanism.

Question 246

Which Segment Routing protection mechanism provides local repair without requiring a separate RSVP-TE signaling protocol?

1. TI-LFA
2. MSDP
3. LDP
4. DHCPv6

Correct Answer: 1

Explanation

Topology Independent Loop-Free Alternate (TI-LFA) provides fast local protection in Segment Routing networks. When a failure occurs, the router can use a precomputed repair path based on Segment Routing instructions to redirect traffic around the failed component. TI-LFA is designed to provide rapid local convergence and does not require RSVP-TE signaling for establishing each repair path. MSDP is related to multicast source discovery, LDP distributes MPLS labels, and DHCPv6 provides IPv6 configuration services. Therefore, TI-LFA is the correct Segment Routing protection mechanism.

Question 247

Which Segment Routing identifier represents a specific adjacency between two nodes?

1. Prefix-SID
2. Node-SID
3. Adjacency-SID
4. Anycast-SID

Correct Answer: 3

Explanation

An Adjacency-SID identifies a specific adjacency from one Segment Routing node to a directly connected neighbor. It can be used when traffic engineering requires traffic to follow a particular link rather than simply reaching a destination prefix. A Prefix-SID identifies a prefix, and a Node-SID is commonly associated with a node’s prefix. An Anycast-SID can represent a shared destination reachable through multiple nodes. Therefore, Adjacency-SID is the correct identifier for representing a specific link or adjacency.

Question 248

Which Segment Routing concept defines the range of labels reserved for Segment IDs within an SR-MPLS domain?

1. SRGB
2. VRF
3. RD
4. LFIB

Correct Answer: 1

Explanation

The Segment Routing Global Block (SRGB) defines a range of MPLS label values reserved for Segment Routing SIDs. Prefix-SIDs and other globally significant SIDs can be represented within this block according to the network’s Segment Routing configuration. Consistent SRGB planning helps ensure that SIDs have predictable meanings across the network. A VRF provides routing-table separation, an RD makes VPN routes unique, and the LFIB contains MPLS forwarding information. Therefore, SRGB is the correct concept for defining the SID label range.

Question 249

Which EVPN mechanism allows a PE to advertise that it is connected to a particular Ethernet Segment?

1. Ethernet Segment Identifier
2. Route Distinguisher
3. MPLS TC
4. OSPF Cost

Correct Answer: 1

Explanation

An Ethernet Segment Identifier (ESI) uniquely identifies an Ethernet Segment in an EVPN multihoming environment. PE routers connected to the same customer Ethernet Segment use the ESI to coordinate multihoming operations, including Ethernet Segment discovery and Designated Forwarder procedures. This allows the EVPN control plane to understand which PE devices participate in the same multihomed segment. The Route Distinguisher identifies VPN routes uniquely, MPLS TC carries traffic-class information, and OSPF cost influences IGP path selection. Therefore, Ethernet Segment Identifier is correct.

Question 250

Which EVPN feature helps prevent duplicate forwarding of BUM traffic toward a multihomed Ethernet Segment?

1. MAC Mobility
2. DF election
3. Route Target import
4. ARP inspection

Correct Answer: 2

Explanation

Designated Forwarder (DF) election determines which PE should forward certain Broadcast, Unknown Unicast, and Multicast traffic toward a multihomed Ethernet Segment. This prevents multiple PE routers from independently forwarding the same BUM traffic onto the customer segment, which could create duplicate frames and Layer 2 loops. MAC Mobility handles changes in MAC location, Route Target import controls VPN route membership, and ARP inspection is a security mechanism. Therefore, DF election is the correct EVPN feature for preventing duplicate BUM forwarding.

Question 251

Which EVPN feature allows a MAC address to move from one PE to another while helping the network detect the change?

1. MAC Mobility
2. LDP
3. BFD
4. Route Dampening

Correct Answer: 1

Explanation

EVPN MAC Mobility provides mechanisms for handling situations where a MAC address moves between different attachment points or PE routers. EVPN uses mobility information, including sequence values, to determine the most recent location of a MAC address and reduce problems caused by stale forwarding information. This is particularly useful in environments where virtual machines or endpoints can move between locations. LDP distributes MPLS labels, BFD detects failures, and Route Dampening addresses unstable BGP routes. Therefore, MAC Mobility is the correct EVPN feature.

Question 252

Which EVPN route type is associated with Inclusive Multicast Ethernet Tag information?

1. Type 1
2. Type 2
3. Type 3
4. Type 5

Correct Answer: 3

Explanation

EVPN Route Type 3 is the Inclusive Multicast Ethernet Tag (IMET) route. It provides information used to establish inclusive multicast trees for forwarding Broadcast, Unknown Unicast, and Multicast traffic across an EVPN network. This is particularly important when EVPN services are deployed over MPLS or other transport technologies that require a control-plane mechanism for BUM traffic distribution. Type 1 is Ethernet Auto-Discovery, Type 2 advertises MAC/IP reachability, and Type 5 advertises IP prefixes. Therefore, Route Type 3 is correct.

Question 253

Which network architecture separates the provider transport infrastructure from customer service networks using an overlay model?

1. Underlay/overlay architecture
2. Flat Layer 2 architecture
3. Single-table architecture
4. Host-only architecture

Correct Answer: 1

Explanation

An underlay/overlay architecture separates the physical or routed transport network from the logical services built on top of it. The underlay provides basic IP or MPLS connectivity, while the overlay provides services such as EVPN, VPNs, or other virtualized network functions. This separation can simplify network design because service information does not need to be distributed throughout every transport device. A flat Layer 2 design does not provide the same separation, while single-table and host-only architectures do not describe this service-provider design principle. Therefore, underlay/overlay architecture is correct.

Question 254

Which device role in an MPLS service provider network normally connects directly to customer-facing CE routers?

1. P router
2. PE router
3. Route Reflector only
4. Core switch only

Correct Answer: 2

Explanation

A Provider Edge (PE) router connects the service provider network to customer-edge (CE) devices. The PE maintains customer-specific service information, such as VRFs for MPLS Layer 3 VPNs, and participates in the relevant control-plane protocols. P routers operate within the provider core and generally do not maintain customer VPN routing information. A Route Reflector is a BGP control-plane scalability function and is not necessarily customer-facing. Therefore, the PE router is the correct device role for connecting directly to customer CE routers.

Question 255

Which device in a traditional MPLS VPN architecture normally forwards labeled packets inside the provider core without maintaining customer VRFs?

1. CE
2. PE
3. P router
4. Customer firewall

Correct Answer: 3

Explanation

A Provider (P) router operates within the MPLS provider core and generally forwards packets using the provider’s transport information without maintaining individual customer VRFs. P routers participate in the provider’s IGP and MPLS forwarding infrastructure, allowing them to transport traffic between PE routers. PE routers maintain customer-specific service information and connect to CE devices. A CE router belongs to the customer network and normally does not participate in the provider’s internal MPLS VPN control plane. Therefore, the P router is correct.

Question 256

Which protocol is commonly used as the IGP in an MPLS Segment Routing provider core?

1. OSPF or IS-IS
2. IGMP only
3. LACP only
4. RADIUS only

Correct Answer: 1

Explanation

OSPF and IS-IS can both serve as Interior Gateway Protocols in an MPLS Segment Routing provider core. Segment Routing information, including SIDs and related attributes, can be advertised through extensions to supported IGPs. The IGP provides the underlying topology and reachability information that Segment Routing uses to construct forwarding paths. IGMP handles multicast membership, LACP manages link aggregation, and RADIUS provides authentication services. Therefore, OSPF or IS-IS is the correct choice for an IGP supporting Segment Routing in a provider core.

Question 257

Which network-management technology uses a push-based model to deliver operational data continuously to a collector?

1. Streaming telemetry
2. Traditional SNMP polling
3. TFTP
4. Telnet

Correct Answer: 1

Explanation

Streaming telemetry uses a push-based approach in which network devices continuously send selected operational information to a telemetry collector. This can provide near-real-time visibility into interface counters, routing state, resource utilization, and other operational metrics. Traditional SNMP polling generally follows a pull-based model in which the management system periodically requests information from devices. TFTP transfers files, while Telnet provides remote terminal access. Streaming telemetry is therefore better suited to continuous data delivery and high-frequency monitoring requirements.

Question 258

Which data format is commonly used by RESTCONF when exchanging structured network-management data?

1. JPEG
2. JSON
3. MPEG
4. SMTP

Correct Answer: 2

Explanation

JSON is commonly used by RESTCONF to represent structured configuration and operational data modeled with YANG. RESTCONF operates over HTTP and provides REST-style access to network resources. Depending on implementation and request headers, XML can also be used, but JSON is widely used because of its compact structure and compatibility with modern automation applications. JPEG is an image format, MPEG is associated with multimedia encoding, and SMTP is an email transport protocol. Therefore, JSON is the correct choice for a commonly used RESTCONF data representation.

Question 259

Which automation technology is commonly used to define network configuration and services using reusable declarative templates?

1. Cisco NSO
2. ARP
3. PIM
4. LACP

Correct Answer: 1

Explanation

Cisco NSO provides service orchestration and network automation capabilities and can use service models to represent desired network services. Reusable templates and models allow operators to automate configuration across multiple devices while maintaining consistency. NSO can interact with devices using protocols and mechanisms such as NETCONF, RESTCONF, and CLI adapters depending on the environment. ARP resolves IPv4 addresses, PIM provides multicast routing, and LACP manages link aggregation. Therefore, Cisco NSO is the correct technology for model-driven network service orchestration and reusable automation.

Question 260

Which protocol is commonly used by Ansible to manage Cisco network devices through structured network-management interfaces when supported?

1. NETCONF
2. IGMP
3. PIM
4. BFD

Correct Answer: 1

Explanation

Ansible can use NETCONF to manage supported network devices through structured configuration interfaces. NETCONF works with YANG-based data models and provides mechanisms for retrieving and modifying configuration data in a structured manner. This can make automation more predictable than relying solely on unstructured CLI commands. IGMP is used for multicast group membership, PIM provides multicast routing, and BFD provides rapid failure detection. Therefore, NETCONF is the correct protocol among the choices for structured Ansible-based network configuration when supported by the target platform.