Cisco DevNet Associate 200-901 (200-901) — Questions 226–300

Meraki is a cloud-managed platform with the described API characteristics.

A CNAME record creates an alias that points to the canonical name. The A record points to an IP address, not another domain.

An access port expects to receive and send only untagged frames, as it belongs to a single VLAN (VLAN 10). If the connected device sends 802.1Q tagged frames, the switch will drop them because the access port does not process VLAN tags. This explains why the port is up/up but not forwarding traffic.

A timeout error in an Ansible playbook during a CI/CD pipeline typically indicates that the network device is responding too slowly to complete the SSH or API session within the configured timeout period. Heavy CPU load on the device can cause delayed responses to Ansible's control node, triggering the timeout before the playbook finishes applying the configuration. This is distinct from connectivity failures or authentication issues, which produce different error messages.

`git commit --amend` modifies the most recent commit by replacing it with a new commit that incorporates staged changes or an updated commit message, effectively rewriting the commit history. `git rebase -i` (interactive rebase) allows you to reorder, squash, edit, or drop commits, which also rewrites the commit history by creating new commit objects.

Content-Type indicates the media type of the request body. Accept indicates the desired response format. Authorization carries credentials.

The client-server constraint is a fundamental principle of REST, as defined by Roy Fielding in his doctoral dissertation. It separates the user interface concerns from data storage concerns, improving portability across multiple platforms and scalability by simplifying server components. This separation allows each side to evolve independently, which is a core architectural benefit.

HTTPS uses TLS (Transport Layer Security) to encrypt HTTP traffic and verify server identity.

In dial-out streaming, the network device (server) initiates the connection to the collector (client).

Cisco IOS XE provides comprehensive REST APIs through its RESTCONF and NETCONF interfaces, enabling programmatic configuration and monitoring of network devices. Cisco DNA Center offers a rich set of REST APIs for intent-based networking, allowing automation of network design, provisioning, policy, and assurance tasks. Both platforms are designed for modern network programmability and are key components of Cisco's DevNet ecosystem.

The `docker build` command reads the instructions in a Dockerfile and assembles a Docker image layer by layer. Each instruction in the Dockerfile (e.g., FROM, RUN, COPY) creates a new layer that is cached and reused, making subsequent builds faster. This is the standard and only command designed specifically for building images from a Dockerfile.

SW1's trunk port is configured with 'switchport trunk allowed vlan 10', which explicitly permits only VLAN 10 traffic. Since VLAN 20 is not in the allowed list, frames from VLAN 20 (including traffic to the server) are dropped at the trunk egress on SW1. This prevents SW1 hosts in VLAN 10 from reaching the VLAN 20 server on SW2, even though the trunk is up and both VLANs exist on both switches.

Setting `serial: 1` in an Ansible playbook forces the play to execute against only one host at a time, even if the play targets multiple switches. This ensures that VLAN configuration is pushed to exactly one switch before moving to the next, preventing network disruption from simultaneous changes.

LoadBalancer provisions a cloud load balancer and assigns a stable external IP, making the service accessible from outside the cluster.

The endpoint /dna/intent/api/v1/network-device/{id} retrieves detailed information for a specific network device, including its management IP address, reachability status, and other attributes. The JSON response showing 'Switch-A' with status 'unreachable' indicates a single-device query, which matches the path parameter {id} used to target a particular device. This endpoint returns a device-level status field (e.g., 'reachabilityStatus') that directly reflects the 'unreachable' value seen in the response.

*args captures positional arguments as tuple (1,2,3), sum is 6, kwargs dict includes {'offset':10}, .get returns 10, total 16.

The data plane is responsible for forwarding packets based on information in the forwarding table, such as destination MAC address for Layer 2 switching. Applying ACLs is also a data plane function because ACL rules are evaluated in hardware or software during packet forwarding to permit or deny traffic.

The 201 Created status code is the correct response for a POST request that successfully creates a new resource. According to RFC 7231, the server should respond with 201 and include a Location header pointing to the newly created resource's URI. This is the standard behavior for RESTful APIs when a POST operation results in resource creation.

TCP (Transmission Control Protocol) is correct for reliable data transfer because it provides connection-oriented communication with sequencing, acknowledgments, and retransmission of lost packets, ensuring data arrives intact and in order. This makes it ideal for microservices that need guaranteed delivery, such as database transactions or order processing.

The intermittent 'Connection refused' errors are caused by the database pod being repeatedly killed due to exceeding its memory limit (512Mi), which triggers OOMKilled restarts. During the restart window, the database pod is unavailable, and the backend's connection attempts to the ClusterIP service (which resolves to the pod's IP) fail because no pod is ready to accept connections. The frequent restarts create a pattern of temporary unavailability that aligns with the observed symptoms.

kubectl describe pod my-pod shows detailed information including events and container statuses. kubectl logs my-pod shows container logs. The other commands are for different resources or abstract actions.

gRPC is correct because it is designed for high-performance, real-time streaming of telemetry data using HTTP/2 and Protocol Buffers. Network devices like Cisco IOS XR and NX-OS use gRPC to push telemetry data to collectors in a continuous stream, eliminating the need for polling and reducing latency.

Cisco native models and OpenConfig models are both valid. IETF models are also valid but not listed. The others are not YANG models.

Squash merging combines all commits into one; using --squash option on merge accomplishes this.

The 'for item in list' loop iterates directly over each element, making it the simplest and most readable for processing each hostname.

YANG (RFC 6020/7950) allows you to define data constraints such as ranges, mandatory elements, and type restrictions directly in the model. When you attempt to apply configuration via NETCONF or RESTCONF, the server validates the data against these constraints before committing, preventing invalid changes from being applied.

The Cisco APIC REST API requires the JSON body for creating a tenant to follow the object model structure: the top-level key is the managed object class (fvTenant), which contains an 'attributes' object with the 'name' property. The name must match the tenant name in the URL (testtenant), and the API expects lowercase for the name value unless the object model specifies otherwise.

It directly translates the list comprehension into an equivalent for-loop with a conditional append. The comprehension `[x**2 for x in range(20) if x % 2 == 0]` iterates over numbers 0–19, filters for even numbers (x % 2 == 0), squares each, and collects the results in a list. Option A's explicit loop and conditional produce the exact same sequence of appended values.

Meraki requires the API key in the X-Cisco-Meraki-API-Key header.

The NETCONF RPC reply indicates a validation failure, which typically occurs when the data being configured does not conform to the YANG model's constraints. In this context, the MTU value provided is outside the allowed range defined in the YANG model for the interface, triggering a validation error before any configuration is applied.

To send a message to a person, use the toPersonEmail parameter instead of roomId.

The private IPv4 ranges are 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. 169.254.0.0/16 is link-local (APIPA).

The 405 Method Not Allowed response indicates that the HTTP method (PUT) is recognized but not supported for the specific resource. In RESTCONF, PUT is used for full resource replacement, but Cisco IOS XE often restricts PUT on certain configuration resources like interface IP addresses because they are nested leafs or lists that require partial updates. PATCH is the correct method for modifying specific fields without replacing the entire resource, aligning with RFC 8040 for partial resource modifications.

LLDP (IEEE 802.1AB) and CDP (Cisco Discovery Protocol) are Layer 2 protocols that allow network devices to advertise their identity, capabilities, and directly connected neighbors. In automation environments, these protocols enable dynamic discovery of the network topology without manual intervention, making them essential for automated inventory and mapping.

Cisco DNA Center uses token-based authentication following the OAuth 2.0 framework. After obtaining a token via the /dna/system/api/v1/auth/token endpoint, the token must be included in the Authorization header using the Bearer scheme (e.g., 'Authorization: Bearer <token>') for all subsequent API requests to prove the client's identity and authorization.

Replacing complex conditionals with polymorphism aligns with the Open/Closed Principle, allowing each subclass to handle its own behavior without modifying existing code. This refactoring technique directly addresses the maintainability issue of deeply nested if-else statements by delegating decision logic to polymorphic method dispatch, which is a core object-oriented design pattern tested in the 200-901 exam.

An emptyDir volume is created empty when a pod is scheduled and can be mounted by multiple containers in the same pod, allowing them to share files.

Ansible is the best-suited tool because it provides a dedicated module (cisco.aci.aci_rest) that directly interacts with the APIC REST API, allowing declarative automation of VLAN and other ACI configurations. Unlike generic scripting, Ansible abstracts the HTTP requests and handles idempotency, authentication, and error handling natively for the ACI fabric.

REST API best practices dictate that URIs should represent resources (nouns), not actions. For example, '/users' or '/orders' clearly identifies the resource being manipulated, while verbs like '/getUsers' or '/createOrder' are discouraged as they conflate the resource with the operation.

GET /dna/intent/api/v1/network-device returns the device inventory.

UDP is a connectionless transport layer protocol that provides minimal overhead, making it ideal for applications like DNS and DHCP that require fast, lightweight communication. DNS uses UDP for queries (port 53) and DHCP uses UDP for client-server exchanges (ports 67/68) because they can tolerate occasional packet loss and benefit from the reduced latency.

Layer 2 (Data Link) uses MAC addresses for local delivery.

NETCONF (Network Configuration Protocol) uses SSH as its default transport protocol, as specified in RFC 6242. SSH provides the required secure, authenticated, and encrypted channel for NETCONF sessions, ensuring confidentiality and integrity of configuration data exchanged between the client and server.

Parameterized queries separate SQL logic from data, preventing attackers from injecting malicious SQL. Input validation is also important but not a direct prevention of SQL injection.

RESTful APIs use resource-based URLs (e.g., /users/123) to uniquely identify resources, which aligns with the uniform interface constraint of REST. This design makes the API intuitive and self-descriptive, allowing clients to interact with resources directly via the URL structure.

A 201 status indicates successful creation, and response.json() parses the JSON body into a Python dict.

Channels 1, 6, and 11 are the only non-overlapping channels in 2.4 GHz.

NETCONF defines standard operations: <get>, <get-config>, <edit-config>, <copy-config>, <delete-config>, <lock>, <unlock>, <close-session>, <kill-session>. <commit> is used in the candidate configuration model but is not a base operation; it's an optional capability. <rpc> is the message wrapper, not an operation.

The Meraki API returns a 400 error with 'network is not ready' because creating a network is an asynchronous operation. The network's underlying infrastructure (e.g., virtual LANs, DHCP scopes, firewall rules) must be fully provisioned before it can accept SSID configurations. Attempting to configure an SSID immediately after creation fails because the network is still in a 'pending' or 'provisioning' state, requiring a polling delay or retry logic.

The GET /dna/intent/api/v1/business/sda/fabric-site API call retrieves the current configuration of fabric sites, allowing the team to validate that fabric devices are correctly provisioned and associated with the intended site. This aligns with the intent-based API model where GET operations are used for validation and monitoring of deployed policies.

The HTTP 429 status code indicates rate limiting has been exceeded. The Meraki API enforces rate limits to protect its infrastructure, and the SDK's built-in retry mechanism with exponential backoff is the correct way to handle this, as it automatically waits increasing intervals between retries, respecting the Retry-After header if present.

/24 means subnet mask 255.255.255.0. Network address is 192.168.1.0, broadcast is 192.168.1.255. Usable hosts range from .1 to .254.

The control plane (decides traffic flow) and data plane (forwards traffic) are the two key planes in SDN, with the controller centralizing the control plane.

Dependabot is the correct GitHub-native tool for automatically scanning dependencies for known vulnerabilities on every push. It monitors the dependency manifest files (e.g., package.json, requirements.txt) against the GitHub Advisory Database and opens pull requests to update vulnerable packages. This directly meets the requirement of scanning dependencies for known vulnerabilities in a CI/CD workflow.

The Cisco Catalyst Center intent API uses a base URL that includes the Catalyst Center hostname (or IP address) and port (typically 443 for HTTPS). For example, the base URL is formatted as `https://<catalyst-center-hostname>:443/dna/intent/api/v1/`. This is required to direct API calls to the specific Catalyst Center instance.

RESTCONF uses the '/restconf/data' base path to retrieve configuration data (the 'data' resource), and the correct Content-Type for RESTCONF with JSON encoding is 'application/yang-data+json', as defined in RFC 8040. This combination ensures the request targets the operational or configuration datastore and specifies the YANG-encoded JSON media type.

PATCH is used for partial updates, PUT for full replacement.

Cisco DNA Center uses Basic Authentication to authenticate to the /dna/system/api/v1/auth/token endpoint, which returns a token for subsequent API calls.

Trunk links carry traffic for multiple VLANs simultaneously by tagging each frame with a VLAN identifier. This allows a single physical link to transport traffic from different VLANs between switches or between a switch and a router. Option C is correct because the primary purpose of a trunk is to multiplex VLAN traffic over one link.

The Link header with rel="next" is used by the Meraki Dashboard API and others for cursor-based pagination.

VXLAN overlays with a distributed virtual switch provide Layer 2 isolation across multiple hosts by encapsulating Ethernet frames in UDP packets (RFC 7348). This creates independent virtual networks (VXLAN segments) that can span hosts, ensuring traffic between containers on the same host is isolated from other tenants without relying on physical network topology.

B is correct because Ansible is an automation tool that uses playbooks (YAML-based) to define a desired network state and can enforce compliance by comparing the current device configuration against the defined state using modules like `ios_config` or `nxos_config`. It is widely used for network compliance checking due to its agentless architecture and idempotent behavior.

D is correct because the PUT request to the RESTCONF endpoint with the provided JSON payload is an idempotent operation. Since the interface GigabitEthernet1/0/1 already exists with the exact same configuration (IP address 10.10.10.1/24), the PUT request effectively replaces the resource with the same data, resulting in no change. RESTCONF uses the HTTP PUT method to create or replace a resource, and if the resource already exists and the payload matches, the operation succeeds without modification.

Cisco DNA Center uses Basic Authentication with username and password (Base64 encoded) in the Authorization header to obtain a token via POST /dna/system/api/v1/auth/token.

Route summarization (also known as route aggregation) allows the router to advertise a single, less specific prefix (e.g., a /22 or /20) that covers multiple contiguous /24 subnets, thereby reducing the number of BGP routes in the routing table while still providing reachability to all the underlying subnets. This technique is commonly implemented on BGP neighbors using the `aggregate-address` command in Cisco IOS, which creates a summary route in the BGP table and suppresses the more specific routes.

The 'upstream timed out' error in a Kubernetes environment behind a Cisco APIC load balancer indicates that the load balancer is attempting to forward traffic to a pod that is not ready to accept connections. Without a Readiness probe, Kubernetes assumes the pod is ready as soon as it starts, but the application may still be initializing or unable to handle requests. The APIC load balancer then sends traffic to an unready pod, causing timeouts and 503 errors.

The URL capability (urn:ietf:params:netconf:capability:url:1.0) is a standard NETCONF capability that allows a client to specify a URL as the source or target of operations like <copy-config> or <edit-config>. Option D is correct because urn:ietf:params:netconf:base:1.0 is the mandatory base capability that every NETCONF session must advertise, as defined in RFC 6241, indicating support for the core NETCONF protocol operations.

The group policy 'Block Social Media' references a content filtering rule that likely uses a predefined or custom URL category list. If the rule blocks only specific URL patterns (e.g., 'instagram.com') but does not include all social media sites (e.g., 'facebook.com'), then users can still access unblocked sites. Meraki content filtering operates on URL category matching or explicit URL pattern lists; if the list is incomplete, the policy will not block all intended sites.

The correct order is: build the image, run tests, then push only if tests pass. Pushing before tests could push a broken image.

json.loads() converts a JSON string into a Python object (dict, list, etc.).

The Link header includes URLs for next, previous, first, and last pages for cursor-based pagination.

The HTTP 400 status code indicates a client-side error, and the response body explicitly states 'Invalid JSON: unexpected token at position 42'. This means the request body contains malformed JSON. A JSON validator (e.g., jsonlint.com, jq, or a library like `json.loads()` in Python) will parse the JSON and pinpoint the exact syntax error (e.g., a missing comma, extra brace, or unescaped quote) at the specified position, allowing the developer to fix the request body quickly.

The GET /v1/people/me endpoint returns the authenticated user's details.