350-501 Automation and Assurance — Timed 15 Questions

Question 1

A network engineer wants to automate the backup of router configurations using Python and NETCONF. Which YANG model should the engineer use to access the running configuration?

Answer

urn:ietf:params:netconf:capability:rollback-on-error:1.0

Answer

urn:ietf:params:netconf:capability:candidate:1.0

Answer

urn:ietf:params:netconf:capability:confirmed-commit:1.0

Answer

urn:ietf:params:netconf:capability:xpath:1.0

Answer

urn:ietf:params:netconf:capability:writable-running:1.0 [correct]

Question 2

Which TWO actions are required to enable model-driven telemetry on a Cisco IOS XR router?

Accepted Answer

Configure a subscription that refers to a sensor group and a destination group.. To enable model-driven telemetry, you must configure a destination group (receiver) and a subscription that ties the sensor path to the destination. Option A is correct because a subscription binds a sensor group and a destination group. Option D is correct because a destination group defines where telemetry data is sent (receiver IP and port). Option B is wrong because an ACL is not required for telemetry; telemetry traffic is initiated by the router. Option C is wrong because NETCONF is not mandatory; telemetry can use gRPC, gNMI, or other protocols. Option E is wrong because the sensor path is configured in a sensor group, not directly in the subscription; the subscription references the sensor group.

Answer

Apply an access-list to allow telemetry traffic from the router.

Answer

Enable NETCONF on the router for telemetry to function.

Answer

Configure the subscription with the sensor path directly.

Question 3

A service provider is implementing network automation using YANG data models. They need to ensure that the automation solution supports both configuration and operational state data retrieval. Which NETCONF operation should be used to retrieve operational state data?

Accepted Answer

. The NETCONF operation retrieves both configuration and operational state data from a device, making it the correct choice for this requirement. Unlike , which only returns configuration data, accesses the running datastore and includes state data such as interface statistics, routing tables, and system status. This aligns with RFC 6241, where is defined as the operation to retrieve combined config and state information.

Answer

<edit-config>

Answer

<get-config>

Answer

<lock>

Question 4

Which tool is used to validate YANG data models against device capabilities and to generate Python bindings for automation scripts?

Accepted Answer

pyang. B is correct because pyang is a YANG data modeling language validator and converter that can validate YANG modules against device capabilities (e.g., via RFC 7895 YANG Library) and generate Python bindings (e.g., using the `--plugindir` or `pyang --format pybind` options) for use in automation scripts. It directly supports the task of validating YANG models and producing Python code, unlike the other options which are protocols or automation frameworks.

Answer

RESTCONF

Answer

Ansible

Answer

NETCONF

Question 5

A network engineer is automating BGP configuration using the Cisco IOS-XE YANG model. They want to enable the 'always-compare-med' feature under BGP. Which XPath expression correctly targets this leaf?

Accepted Answer

/native/router/bgp/scope/global/always-compare-med. The Cisco IOS-XE native YANG model (urn:cisco:params:xml:ns:yang:cisco-native) structures BGP configuration under /native/router/bgp/scope/global/always-compare-med. The 'scope' container is required to differentiate between global and VRF-specific BGP settings, and 'always-compare-med' is a leaf within the global scope. This path accurately reflects the hierarchical model used by Cisco for BGP automation.

Answer

/bgp/global/always-compare-med

Answer

/native/router/bgp/always-compare-med

Answer

/router/bgp/global/always-compare-med

Question 6

A service provider uses RESTCONF to automate interface configuration. They need to add a new IPv4 address to an existing interface. Which HTTP method and URI should be used?

Accepted Answer

PATCH /restconf/data/ietf-interfaces:interfaces/interface=GigabitEthernet0/1/ietf-ip:ipv4/address. PATCH is the appropriate HTTP method for a partial update to an existing resource, and the URI targets the IPv4 address list under the specific interface. This allows adding a new IPv4 address without replacing the entire interface configuration, which aligns with RESTCONF's support for partial resource modification as defined in RFC 8040.

Answer

DELETE /restconf/data/ietf-interfaces:interfaces/interface=GigabitEthernet0/1

Answer

POST /restconf/data/ietf-interfaces:interfaces/interface=GigabitEthernet0/1/ietf-ip:ipv4

Answer

PUT /restconf/data/ietf-interfaces:interfaces/interface=GigabitEthernet0/1/ietf-ip:ipv4/address

Question 7

What is the primary benefit of using model-driven telemetry over traditional SNMP polling for network assurance?

Accepted Answer

Provides real-time data streaming without polling overhead. Model-driven telemetry uses a push model where network devices continuously stream structured data (e.g., YANG-encoded) to a collector, eliminating the need for periodic SNMP polling. This provides real-time visibility with minimal CPU overhead on the device, as the device itself initiates the data export based on configured subscriptions, rather than responding to repeated GET requests.

Answer

Reduces the need for YANG models

Answer

Increases security by using SSH

Answer

Simplifies device configuration

Question 8

A network operator uses gRPC Network Management Interface (gNMI) to collect telemetry data from routers. They notice that some updates are missing. Which gNMI mode should be used to ensure that all state changes are captured?

Accepted Answer

ON_CHANGE. ON_CHANGE mode in gNMI ensures that the target device sends a telemetry update immediately whenever a state change occurs, guaranteeing that no updates are missed. This is in contrast to SAMPLE mode, which only sends periodic snapshots and can miss transient changes between intervals. Therefore, to capture all state changes, ON_CHANGE is the correct subscription mode.

Answer

TARGET_DEFINED

Answer

POLL

Answer

SAMPLE

Question 9

A service provider is deploying a new automation framework using Ansible to configure MPLS VPNs. They need to ensure that the Ansible playbook can handle configuration rollback in case of failure. Which Ansible feature should be used?

Accepted Answer

Use the 'backup' option in the ios_config module. The 'backup' option in the ios_config module instructs Ansible to save a copy of the running configuration to a local file before making any changes. If the playbook fails or produces an undesired state, the operator can restore the device to the previous configuration using that backup file. This provides a straightforward rollback mechanism for MPLS VPN deployments without requiring external version control or manual snapshots.

Answer

Use 'tags' to selectively apply tasks

Answer

Use 'check_mode' to validate changes before applying

Answer

Set 'ignore_errors' to true

Question 10

A network engineer is troubleshooting a NETCONF session that fails to establish between a controller and a router. The router supports NETCONF over SSH on port 830. The controller can reach the router but the session fails. What is the most likely cause?

Accepted Answer

The SSH host key of the router is not in the controller's known_hosts file. The most likely cause is that the SSH host key of the router is not in the controller's known_hosts file. NETCONF over SSH (RFC 6242) requires SSH transport, and the controller must authenticate the router's SSH host key during session establishment. If the host key is missing or mismatched, the SSH handshake fails, preventing the NETCONF session from starting, even though the router is reachable and NETCONF is enabled.

Answer

The router's NETCONF capability is disabled

Answer

The controller is using the wrong port (e.g., 22)

Answer

The router does not support YANG models

Question 11

Which TWO statements about YANG data models are true? (Choose two.)

Accepted Answer

YANG models are used to model data for NETCONF and RESTCONF.. YANG (RFC 6020/7950) is a data modeling language specifically designed to model configuration and state data for network management protocols like NETCONF and RESTCONF. YANG defines the structure, constraints, and semantics of data that can be exchanged via these protocols, making it the standard for model-driven network automation.

Answer

YANG models can be directly converted to SNMP MIBs.

Answer

YANG models define only configuration data, not state data.

Answer

YANG models define CLI commands.

Question 12

Which THREE components are required for model-driven telemetry with gRPC? (Choose three.)

Accepted Answer

YANG data model. YANG data models (C) are required because they define the structure and semantics of the telemetry data being streamed. gRPC uses YANG as its schema language to encode data in Protocol Buffers (protobuf) or JSON format, ensuring the receiver can parse and interpret the telemetry information correctly.

Answer

SNMP trap receiver

Answer

NETCONF session

Question 13

Which TWO statements about Cisco NSO (Network Services Orchestrator) are true? (Choose two.)

Accepted Answer

NSO provides northbound APIs using NETCONF and RESTCONF.. NSO provides northbound APIs using NETCONF and RESTCONF, enabling integration with higher-level orchestration and management systems. These standard protocols allow external systems to interact with NSO for service lifecycle management, configuration, and operational data retrieval, making B correct.

Answer

NSO automatically generates Python scripts for device configuration.

Answer

NSO eliminates the need for SNMP in network management.

Answer

NSO only supports CLI-based device management.

Question 14

You are a network automation engineer for a large service provider. Your team is tasked with automating the provisioning of new MPLS L3VPN services across a multi-vendor environment (Cisco and Juniper). The automation framework uses Ansible with Jinja2 templates and NETCONF as the transport protocol. During a pilot deployment, the automation successfully configures the Cisco devices but fails on Juniper devices with a 'syntax error' when applying the generated XML configuration. The Jinja2 templates are designed to generate Cisco-style configuration. You need to modify the automation to support both vendors. Which approach is most effective?

Accepted Answer

Use IETF YANG models and create separate Jinja2 templates for Cisco and Juniper that map to their respective native YANG models.. Using IETF YANG models (e.g., RFC 8299 for L3VPN) provides a vendor-neutral data model that both Cisco and Juniper support via NETCONF. Creating separate Jinja2 templates for each vendor ensures the generated XML conforms to each device's native YANG models, avoiding syntax errors. This approach maintains automation consistency while respecting vendor-specific implementations.

Answer

Write a Python script that translates Cisco XML to Juniper XML before sending.

Answer

Switch to CLI-based automation using SSH to avoid XML syntax issues.

Answer

Create a single Jinja2 template that uses conditional statements to generate different XML for each vendor.

Question 15

You are responsible for network assurance for a Tier-1 ISP that has deployed model-driven telemetry using gNMI with ON_CHANGE subscriptions on all core routers. Recently, the NMS team reported that some BGP route flaps are not being captured in the telemetry data, even though the routers' syslogs show the flaps occurred. The telemetry subscription is for the path '/bgp/neighbors/neighbor/state/messages/received'. The NMS is using a gNMI collector that supports both ON_CHANGE and SAMPLE subscriptions. You suspect the issue is with the subscription configuration. Upon reviewing the router configuration, you see that the telemetry subscription uses the SAMPLE mode instead of ON_CHANGE. What is the most appropriate action to ensure all BGP route flap events are captured?

Accepted Answer

Modify the subscription to use ON_CHANGE mode for the BGP neighbor paths.. The gNMI ON_CHANGE subscription mode is designed to stream telemetry updates only when the value of a subscribed path changes. Since the NMS is missing BGP flap events, the subscription must be using SAMPLE mode, which periodically polls the state and can miss transient events between sampling intervals. Changing the subscription to ON_CHANGE ensures that every state transition (e.g., BGP session up/down) is immediately pushed to the collector, capturing all flaps.

Answer

Configure the router to send syslogs to the NMS and parse them for BGP flaps.

Answer

Add a second subscription with ON_CHANGE for the same paths to ensure redundancy.

Answer

Change the subscription to SAMPLE with a 1-second interval to capture flaps more frequently.