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Question 381

Which NETCONF datastore contains the configuration currently being used by the device?

1. Startup
2. Candidate
3. Running
4. Operational

Correct Answer: 3

Explanation

The NETCONF running datastore represents the configuration currently active on the device. Changes made directly to the running configuration can immediately affect device behavior, depending on the implementation and operation being performed. The candidate datastore provides a separate workspace where changes can be prepared before being committed, while the startup datastore contains configuration intended to be loaded during boot. The operational datastore is commonly associated with operational state rather than configuration in model-driven management systems. Therefore, the running datastore is the correct answer.

Question 382

Which NETCONF datastore allows configuration changes to be prepared before being committed to the running configuration?

1. Candidate
2. Running
3. Startup
4. Archive

Correct Answer: 1

Explanation

The NETCONF candidate datastore provides a workspace where configuration changes can be assembled and validated before they are committed to the running configuration. This model is useful because administrators or automation systems can prepare multiple changes as a transaction rather than immediately applying every individual modification. After validation, the changes can be committed according to the device’s supported NETCONF capabilities. The running datastore represents active configuration, while startup contains boot-time configuration. Therefore, candidate is the correct datastore for preparing changes before commitment.

Question 383

Which NETCONF operation applies the configuration from the candidate datastore to the running datastore?

1. Lock
2. Commit
3. Get
4. Validate

Correct Answer: 2

Explanation

The NETCONF commit operation applies changes from the candidate datastore to the running configuration. This transactional approach allows multiple configuration changes to be prepared before they become active. Depending on the implementation, additional operations such as validate can be used to check configuration correctness before committing. Lock is used to control access to a datastore, while get retrieves information from the device. Using commit provides a controlled mechanism for activating prepared configuration changes. Therefore, commit is the correct NETCONF operation.

Question 384

Which NETCONF feature can automatically roll back a configuration if a confirmed commit is not confirmed within the specified time?

1. Candidate locking
2. Confirmed commit
3. Route Refresh
4. Graceful Restart

Correct Answer: 2

Explanation

NETCONF confirmed commit provides a safety mechanism for remote configuration changes. When a confirmed commit is issued, the configuration is temporarily accepted, but it must be confirmed again within the specified timeout. If confirmation does not occur, the device can automatically revert to the previous configuration. This is especially useful when making changes remotely because an incorrect configuration could otherwise disconnect the administrator. Candidate locking controls datastore access, while Route Refresh and Graceful Restart are BGP features. Therefore, confirmed commit is correct.

Question 385

Which YANG statement is used to define a reusable grouping of schema nodes?

1. grouping
2. augment
3. deviation
4. notification

Correct Answer: 1

Explanation

The YANG grouping statement defines a reusable collection of schema nodes that can be incorporated elsewhere using uses. This promotes modularity and reduces duplication in YANG data models. The augment statement adds new schema nodes to an existing schema location, while deviation modifies or restricts aspects of a model for a particular implementation. The notification statement defines event notification structures. Therefore, grouping is the correct YANG statement for creating reusable schema components.

Question 386

Which YANG statement is commonly used to add additional schema nodes to an existing data tree?

1. Uses
2. Augment
3. Grouping
4. Import

Correct Answer: 2

Explanation

The YANG augment statement allows a module to add schema nodes to an existing schema tree defined elsewhere. This mechanism is useful for extending standard or vendor-specific models without rewriting the original schema. The grouping statement defines reusable structures, while uses incorporates a previously defined grouping. import makes definitions from another YANG module available for reference. Therefore, augment is the correct statement for extending an existing YANG schema.

Question 387

Which RESTCONF HTTP method is generally used to retrieve configuration or operational data without modifying the resource?

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

Correct Answer: 3

Explanation

The HTTP GET method is used by RESTCONF to retrieve resources without modifying them. A client can use GET to obtain configuration or operational data represented according to the relevant YANG model and RESTCONF resource structure. POST can create resources or invoke operations, PATCH performs partial modifications, and DELETE removes resources. Because GET is intended for retrieval rather than configuration changes, it is commonly used by automation systems to inspect network state before making further changes. Therefore, GET is correct.

Question 388

Which HTTP method is commonly used by RESTCONF to apply a partial modification to an existing resource?

1. GET
2. PATCH
3. DELETE
4. OPTIONS

Correct Answer: 2

Explanation

RESTCONF commonly uses the HTTP PATCH method for partial modification of an existing resource. Instead of replacing the entire resource, PATCH allows a client to modify selected portions of the configuration. This is useful for automation because only the required configuration elements need to be changed. GET retrieves information, DELETE removes a resource, and OPTIONS can provide information about supported HTTP methods. Using PATCH appropriately can reduce unnecessary configuration changes and help automation systems make targeted updates. Therefore, PATCH is the correct answer.

Question 389

Which telemetry approach continuously streams network data to a collector rather than requiring repeated polling requests?

1. Streaming telemetry
2. SNMP polling
3. CLI scraping
4. FTP transfer

Correct Answer: 1

Explanation

Streaming telemetry continuously sends selected operational data from a network device to a telemetry collector. This differs from traditional SNMP polling, where a management system periodically asks devices for values. Streaming telemetry can provide more frequent and near-real-time visibility into interface statistics, routing state, resource utilization, and other operational information. It can also reduce the inefficiency associated with repeated polling of large sets of data. CLI scraping and FTP are not equivalent telemetry mechanisms. Therefore, streaming telemetry is correct.

Question 390

Which protocol is commonly associated with model-driven streaming telemetry and supports subscription-based telemetry?

1. gNMI
2. SMTP
3. TFTP
4. Telnet

Correct Answer: 1

Explanation

gNMI, or gRPC Network Management Interface, is commonly used for model-driven network management and streaming telemetry. It supports subscription mechanisms through which a client can request ongoing updates for selected data paths. gNMI commonly works with structured data models such as YANG and is widely used in modern automation and telemetry architectures. SMTP is an email protocol, TFTP provides simple file transfer, and Telnet provides remote terminal access. Therefore, gNMI is the correct protocol for subscription-based model-driven telemetry.

Question 391

Which BGP capability allows a router to request a complete set of routes again without resetting the established BGP session?

1. Route Refresh
2. Graceful Restart
3. Add-Path
4. Confederation

Correct Answer: 1

Explanation

BGP Route Refresh allows a router to request that its neighbor resend routing information without resetting the established BGP session. This is particularly useful after changing inbound routing policies because the newly received routes can be processed according to the updated policy. Route Refresh improves operational flexibility and avoids unnecessary session disruption. Graceful Restart is designed to preserve forwarding during certain control-plane restart conditions, Add-Path allows multiple paths to be advertised, and Confederations divide an autonomous system into internal sub-AS structures. Therefore, Route Refresh is correct.

Question 392

Which BGP feature can allow a router to accept its own AS number in the AS_PATH under controlled circumstances?

1. Next-Hop-Self
2. Allowas-in
3. Route Refresh
4. Add-Path

Correct Answer: 2

Explanation

The BGP allowas-in feature can permit a router to accept routes containing its own autonomous system number in the AS_PATH. Normally, BGP uses the presence of its own AS number in the AS_PATH as an indication of a routing loop and rejects the route. In certain network designs, such as some multihomed customer or MPLS VPN scenarios, controlled use of allowas-in may be required. Next-Hop-Self changes the BGP next hop, Route Refresh requests route updates, and Add-Path advertises multiple paths. Therefore, allowas-in is correct.

Question 393

Which BGP feature can modify the AS_PATH of a customer route so that a remote site does not reject it because it contains its own AS number?

1. AS Override
2. MED
3. Weight
4. Route Refresh

Correct Answer: 1

Explanation

BGP AS Override is commonly used in MPLS VPN environments where the same customer autonomous system number may appear at multiple sites. A PE router can replace occurrences of the customer’s AS number in the AS_PATH before advertising the route toward another site. This prevents the receiving customer router from rejecting the route because its own AS number appears in the path. MED influences path selection, Weight is locally significant, and Route Refresh requests updated routes. Therefore, AS Override is correct.

Question 394

Which MPLS VPN technique provides controlled route exchange between VRFs on the same PE router?

1. Route leaking
2. Penultimate Hop Popping
3. Label Swapping
4. PHP

Correct Answer: 1

Explanation

VRF route leaking allows selected routes to be exchanged between different VRFs according to configured policy. This can be useful when customers or services need controlled communication across otherwise separate routing tables. Route leaking can be implemented using mechanisms such as import and export policies or other platform-supported techniques. Penultimate Hop Popping and label swapping are MPLS forwarding operations and do not directly provide VRF-to-VRF route exchange. Therefore, route leaking is the correct answer.

Question 395

Which MPLS VPN feature is specifically designed to reduce the number of VPN routes distributed to a PE by controlling which VPN routes are advertised by BGP?

1. RT-Constrain
2. LACP
3. CFM
4. PIM-SSM

Correct Answer: 1

Explanation

Route Target Constraints (RT-Constrain) allow BGP speakers to communicate the Route Targets for which they have interest. VPN routes can then be selectively distributed only toward PEs that need those routes, reducing unnecessary VPNv4 or VPNv6 route propagation. This can significantly improve scalability in large MPLS VPN environments. LACP manages link aggregation, CFM provides Ethernet OAM, and PIM-SSM handles multicast routing. Therefore, RT-Constrain is the correct mechanism for controlling VPN route distribution.

Question 396

Which EVPN route type is used to advertise 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 that allows participating PE routers to establish the necessary forwarding state for BUM traffic within an EVPN instance. BUM stands for Broadcast, Unknown Unicast, and Multicast. Type 1 is Ethernet Auto-Discovery, Type 2 is MAC/IP Advertisement, and Type 5 is IP Prefix Advertisement. Therefore, Type 3 is the correct EVPN route type for IMET information.

Question 397

Which EVPN mechanism helps prevent a multihomed Ethernet segment from receiving a frame back through another PE on the same segment?

1. Split horizon
2. Route Refresh
3. RPKI
4. MED

Correct Answer: 1

Explanation

EVPN split-horizon mechanisms help prevent traffic received from one PE on a multihomed Ethernet Segment from being forwarded back toward the same Ethernet Segment through another PE. This is important for avoiding forwarding loops and duplicate traffic in EVPN multihoming environments. EVPN can use Ethernet Segment identifiers and associated labels or other forwarding information to implement the required split-horizon behavior. Route Refresh is a BGP control-plane function, RPKI validates route origin, and MED influences BGP path selection. Therefore, split horizon is correct.

Question 398

Which Ethernet technology allows multiple VLAN-tagged customer networks to be transported through a provider network using an additional VLAN tag?

1. QinQ
2. LDP
3. RPKI
4. BFD

Correct Answer: 1

Explanation

QinQ, also known as VLAN stacking, allows an additional VLAN tag to be added to frames that already contain a customer VLAN tag. The outer provider tag can identify the service or customer traffic while preserving the customer’s original VLAN information. This allows service providers to transport multiple customer VLANs across their infrastructure without requiring unique provider VLAN assignments for every customer VLAN. LDP distributes MPLS labels, RPKI validates BGP route origins, and BFD provides rapid failure detection. Therefore, QinQ is correct.

Question 399

Which Ethernet service provides a point-to-point Layer 2 connection between two customer endpoints?

1. VPWS
2. VPLS
3. OSPF
4. EVPN Type 3

Correct Answer: 1

Explanation

Virtual Private Wire Service (VPWS) provides a point-to-point Layer 2 service between two customer endpoints across a provider network. The provider transports Ethernet frames between the endpoints while presenting a logical point-to-point connection. VPLS instead provides multipoint-to-multipoint Layer 2 connectivity among multiple sites. OSPF is an IP routing protocol, while EVPN Type 3 is an EVPN control-plane route type rather than a point-to-point Layer 2 service. Therefore, VPWS is correct.

Question 400

Which Layer 2 VPN technology provides multipoint Ethernet connectivity between multiple customer sites over a provider network?

1. VPWS
2. VPLS
3. LDP Discovery
4. BFD

Correct Answer: 2

Explanation

Virtual Private LAN Service (VPLS) provides multipoint Layer 2 connectivity between multiple customer sites over a provider network. It creates a virtual Ethernet switching environment in which geographically separated customer sites can communicate as though they were connected to the same Layer 2 domain. VPWS is designed for point-to-point Layer 2 connectivity, while LDP Discovery and BFD perform control-plane and fault-detection functions rather than providing customer Ethernet services. Therefore, VPLS is the correct answer.