Cisco DevNet Associate 200-901 (200-901) — Questions 451–525

Accessing `data['response']` yields the JSON array, and `[0]` selects its first element, the device object. Indexing that dictionary with `['managementIpAddress']` returns the nested string "192.168.1.1". This directly satisfies the stem's requirement to extract the management IP from the nested structure.

PATCH applies partial modifications to an existing resource, sending only the fields being changed. PUT would replace the entire resource representation, so PATCH uniquely satisfies the stem's requirement to partially update a resource without overwriting unspecified attributes.

HTTP 429 Too Many Requests signals rate limiting. The Meraki Dashboard API enforces a limit of 5 calls per second per organisation; exceeding it returns 429 until the window resets. The Retry-After header indicates how long to wait, so the cause is request volume, not authentication or payload errors.

Claiming into a network requires the serials to exist in the organisation's inventory; the dashboard rejects unknown serials with that 400 error. Meraki devices must first be added to inventory (via order, licence claim, or manual add) before `POST /networks/{networkId}/devices/claim` can bind them, so the script must add inventory first.

2xx status codes indicate success. The request was successfully received, understood, and accepted. For example, 200 OK means the request succeeded. This range is used when the client's request was valid and the server fulfilled it.

Exponential backoff increases the delay between retries, reducing load on the API. Respecting the Retry-After header ensures compliance with the API's rate limit policy. This approach is standard for handling 429 errors and improves the chances of eventual success without causing further throttling. It is both polite and effective.

10.0.0.0/8 sits within the RFC 1918 private addressing space, spanning 10.0.0.0 to 10.255.255.255. It satisfies the stem's requirement for a valid private IPv4 range, unlike public or reserved blocks. Organisations use it for internal networks, with NAT handling external traffic.

The candidate capability means the device supports a candidate configuration datastore that can be edited, validated, and then committed atomically. Combined with confirmed-commit, this allows the developer to stage changes and have them automatically rolled back if the commit is not confirmed, which is exactly the safe configuration workflow described.

The Meraki Dashboard API authenticates every call with a custom header, X-Cisco-Meraki-API-Key, carrying the user-generated key. This satisfies the stem's requirement for the header-based credential, unlike OAuth bearer tokens or basic authentication, which the API does not accept.

Separation of Concerns assigns each module one distinct responsibility, directly satisfying the stem's requirement for a single part of the functionality. Unlike cohesion, which measures how strongly related a module's internals are, this principle prescribes the boundary itself, keeping unrelated functionality isolated so changes in one area do not ripple across others.

An AAAA record maps a hostname to a 128-bit IPv6 address, satisfying the stem's requirement for the address family returned by this record type. It mirrors the A record's role for IPv4 but uses four times the bits, which is why the mnemonic quadruples the letter.

The Cisco DNA Center Intent API provides a GET endpoint at /dna/intent/api/v1/site to retrieve all sites. This endpoint returns a list of sites defined in the network hierarchy. It is a read-only operation that requires authentication via an X-Auth-Token header obtained from the authentication API. This is the correct way to list sites.

The DNA Center intent API exposes Layer 2 topology through the topology/l2 path, and appending the VLAN identifier scopes results to that broadcast domain. Querying this endpoint with GET returns nodes and links for the specified VLAN, matching the requirement.

PATCH applies a partial modification, changing only the fields included in the request body while leaving all other resource properties untouched. This directly satisfies the stem's requirement for a partial update, unlike PUT, which replaces the entire resource representation and would overwrite unspecified fields with defaults or nulls.

GET /v1/people/me returns the authenticated user's own profile, resolving the caller's identity from the OAuth token rather than requiring an explicit person ID. This satisfies the stem's requirement to retrieve the current user's Webex profile information without knowing or supplying their identifier in advance.

Idempotency ensures consistent state.

Using environment variables or a secure vault keeps credentials out of source code, reducing the risk of accidental exposure. It allows for different configurations across environments and facilitates rotation. This is a widely recommended practice for managing secrets in applications.

A Secret of type kubernetes.io/tls stores a TLS certificate and private key and can be mounted as files into a pod via a volume. This keeps sensitive material out of the image and allows the application to read the files at a known path for mutual TLS. Other resources either store non-sensitive data or do not provide file-based injection.

HTTP 201 Created indicates that the request has succeeded and has led to the creation of a new resource. The response typically includes a Location header with the URI of the new resource. This is the correct interpretation for a POST request that creates a resource. It is a success status code in the 2xx range.

HTTP keep-alive, the default in HTTP/1.1, allows a single TCP connection to carry multiple sequential request/response pairs. Reusing the established socket avoids repeating the three-way handshake and TCP slow start for each call, which lowers latency and resource consumption when a client makes several requests to the same server.

The correct endpoint is formed by combining the base URL and the resource path. A GET request to /v1/users retrieves the collection of users. This follows RESTful conventions where GET is used to retrieve data without side effects. The full URL includes the base and the resource, resulting in the correct endpoint.

`socket.getaddrinfo` returns a list of 5-tuples: address family, socket type, protocol, canonical name, and a socket address tuple. With `family=socket.AF_INET` and `type=socket.SOCK_STREAM`, it filters for IPv4 TCP endpoints. Each sockaddr is a (host, port) pair for IPv4. This structure lets a client iterate over candidates and attempt connections without manually parsing DNS responses or constructing sockaddr structures.

SDN separates the control plane from the data plane, letting a controller push configuration programmatically via APIs. This replaces per-device CLI changes, so network configuration changes are automated across the fabric rather than performed manually, satisfying the benefit of reduced manual effort and human error.

The DNA Center Intent API requires obtaining an authentication token by sending a POST request to the /dna/system/api/v1/auth/token endpoint. The request must include Basic Auth headers with the username and password. The response contains a token that must be used in subsequent API calls. This step is essential for authentication and is documented in the Cisco DNA Center Platform API guide.

Checking the status_code allows the script to handle different HTTP responses explicitly. For example, a 200 indicates success, while 404 means the resource was not found, and 500 indicates a server error. By branching logic, the developer can implement retries for 5xx errors or display user-friendly messages for 4xx errors. This is a fundamental practice for robust API interaction.

This snippet correctly accesses the 'response' key from the parsed JSON and iterates over the list of site objects, printing the 'name' field of each. The Cisco DNA Center API returns a JSON object with a top-level 'response' key containing an array of site details, so this approach accurately extracts the required information.

Encrypted secret stores keep values out of the repository and mask them in logs, so pipeline output does not reveal them. Referencing them as variables allows jobs to consume secrets without hardcoding. This directly protects API keys and registry passwords during builds and deployments.

GET retrieves a representation without altering server state, satisfying both safety (no side effects) and idempotence (repeated identical requests yield the same result). Unlike POST, which creates or modifies resources, GET is defined by RFC 9110 as both safe and idempotent, making it the only listed method meeting both constraints.

PATCH applies a partial modification, sending only the description field in the request body while leaving all other device attributes untouched. PUT would replace the entire resource representation, risking unintended overwrites of unmentioned fields. This satisfies the stem's constraint of updating solely the description.

Signing build artifacts with a private key and verifying signatures before deployment ensures tampering between build and release is detected. This satisfies the pipeline's integrity requirement, preventing an attacker who compromises an intermediate repository from injecting altered binaries into production.

VLAN 20 succeeding proves the router's trunk and subinterface configuration works generally, isolating the fault to VLAN 10's subinterface being down or misconfigured. This satisfies the stem's constraint by explaining why only VLAN 10 hosts cannot reach their gateway.

This is correct because requests.get() returns a Response object, and calling .json() on it parses the JSON body into Python data structures. If the payload has a top-level key 'interfaces' containing a list of dictionaries, indexing with ['interfaces'] and iterating yields each interface dict, from which ['name'] extracts the desired field.

NSO's check-sync compares the device's running configuration against the service instance's intended configuration. An out-of-sync result means pe1's actual config has drifted from what the vpn1 service model specifies, so a re-deploy or reconcile action is needed to restore alignment.

A concurrent write by another client triggers HTTP 409 Conflict because NX-OS detects a stale configuration revision, rejecting the update to prevent overwriting newer changes. This satisfies the stem's requirement for a scenario causing the conflict, since the resource's version no longer matches the client's submitted payload.

Gig0/1 shows Status down and Protocol down.

`application/yang-data+json` is the media type RESTCONF mandates for JSON-encoded YANG data, as defined in RFC 8040. It satisfies the stem's JSON encoding constraint by pairing the `+json` structured suffix with the `yang-data` subtype, letting the server parse the payload against the YANG schema rather than treating it as generic JSON.

Ansible resolves variables from inventory host_vars and group_vars, making device-specific values available to tasks. Defining them there ensures the playbook references resolve correctly for each switch. This is the standard mechanism for supplying per-device data such as management addresses and platform-specific settings.

Hard-coded credentials in pipeline definitions, scripts or repositories leak through logs and version history. A vault keeps secrets encrypted and access-controlled, injecting them only into the running job, so the pipeline never persists plaintext credentials in build artefacts or source control.

HTTP 404 means the server received and understood the request but found no resource matching that URI. The endpoint path is wrong or removed, so the server cannot map it to a handler. This directly satisfies the stem's 404 symptom, unlike authentication or server errors.

Mocking external HTTP requests prevents tests from depending on network availability or API rate limits. It allows you to simulate various responses, including errors, and ensures tests run quickly and deterministically. This isolation is crucial for reliable unit tests, as it removes external dependencies and focuses on the function's logic.

GitFlow defines a long-lived develop branch that accumulates merged feature branches, with release branches cut from develop for stabilisation before merging into main. This matches the stem's described structure precisely, unlike trunk-based or GitHub Flow.

Cisco DNA Center uses token-based authentication. The developer must send a POST request to the '/dna/system/api/v1/auth/token' endpoint with the username and password encoded in Base64 in the Authorization header. The response contains a token that must be included in subsequent API calls as 'X-Auth-Token'. This is the standard method for DNA Center API authentication.

Configuring Basic Auth on the Authorization tab injects the credentials as a Base64-encoded `Authorization: Basic` header on every request, satisfying the stem's requirement to test a Basic-authenticated API. Postman handles encoding automatically, so the username and password need not be manually concatenated or encoded before sending.

Network congestion occurs when the volume of traffic exceeds the capacity of a link or device, causing packets to be buffered and delayed. This results in increased latency without necessarily causing packet loss. Traceroute would show increased round-trip times at the congested hop, while packets still reach the destination.

Kubernetes Secrets hold sensitive data separately from the pod spec and image, satisfying the requirement to avoid hard-coding the API key. Mounting it as an environment variable injects the credential at runtime, so the container authenticates to the third-party API without exposing the key in source control or the image layer.

A PersistentVolumeClaim binds to a PersistentVolume, decoupling storage lifecycle from the pod so data survives pod deletion and rescheduling. This satisfies the stem's requirement for storage persisting beyond the pod lifecycle, unlike emptyDir or hostPath, which are tied to the pod or node.

Creating a message is a resource-creation action, so the Webex messaging API expects an HTTP POST to the /v1/messages collection endpoint. The target room is identified by passing roomId in the JSON request body, which routes the message to that specific room.

A config file excluded by .gitignore is never committed, so the secret does not enter the repository history. Each environment supplies its own file, and the parsing code can be committed safely because it contains no secret values, satisfying the requirement while remaining convenient for other teams.

TCP provides connection-oriented, reliable delivery: sequence numbers, acknowledgements and retransmission recover lost or reordered segments, and flow control prevents overwhelming the receiver. This guarantees the integrity of large transfers, which the unreliable, best-effort UDP cannot.

Rebasing a feature branch onto the main branch rewrites the feature branch's commits to apply on top of the latest main, resulting in a linear history when merged. This avoids merge commits and keeps the commit graph clean. It is a common practice in teams that prefer a linear history, though it should be used with caution on shared branches.

Intersight's API Key with HMAC signing authenticates each programmatic request using a key ID and secret, avoiding interactive browser sign-in or stored passwords. This suits automated provisioning scripts, satisfying the requirement for secure non-interactive access to the UCS management platform.

The provider parameter supplies the transport and authentication details the module needs to reach the device, such as host, username, password and connection type. Without it, ios_config cannot establish the session required to push configuration changes to the IOS XE device.

Ansible's agentless architecture pushes declarative configuration over SSH, letting a single playbook apply identical VLAN definitions across many switches simultaneously. This directly satisfies the stem's requirement to automate deployment across multiple devices, unlike manual CLI entry or per-device scripting, and needs no software installed on the switches themselves.

Modifying the existing NetworkPolicy to add an ingress rule that allows pods with label 'app: backend' is the correct approach. It permits the needed traffic while preserving the existing restriction that only 'app: frontend' pods are allowed by default. This is the most secure and appropriate solution.

NETCONF uses YANG-modelled datastores and RPC operations to configure and retrieve device state, satisfying the stem's requirement for model-driven programmability. Unlike SNMP's MIBs or CLI scraping, NETCONF's protocol operations map directly onto YANG schema nodes, giving structured, transactional configuration rather than imperative command sequences.

This securityContext sets runAsNonRoot to true, which ensures the container does not run as UID 0, and readOnlyRootFilesystem to true, which mounts the root filesystem as read-only. These are the exact settings required to enforce the security policies. They can be applied at the pod or container level, but container-level is more granular.

DNA Center provides a token endpoint at /dna/system/api/v1/auth/token. The developer sends a POST with Basic Auth credentials to receive a time-limited token, which is then used in the X-Auth-Token header for subsequent API calls. This is the correct token-based method and avoids hardcoding credentials in each request.

GET /v1/people/me returns the authenticated user's own profile, resolving identity directly from the bearer token rather than requiring a person ID. This satisfies the stem's requirement to retrieve the current user's details without first querying another endpoint to discover their identifier.

RESTCONF encodes data as either XML or JSON, negotiated through the Accept and Content-Type headers. This satisfies the stem's requirement for the format typically supported when retrieving operational data, since RESTCONF, unlike SNMP or NETCONF's XML-only encoding, permits JSON payloads alongside XML.

Ansible is agentless and push-based: the control node executes playbooks and connects to managed devices over SSH to apply tasks. This matches the described architecture exactly, since no software agent must be installed on the Cisco devices and the central server initiates every change.

Syslog is a push mechanism, so the device sends events to a collector without polling. The collector can parse the message and call the Slack API webhook to notify the bot. This is a standard event-driven pattern that matches the requirement for near real-time notification.

The Link response header returns RFC 5988 web-linking metadata, including rel="next", rel="prev", rel="first" and rel="last" URLs. This satisfies the stem's pagination constraint: Meraki's API caps results per page, so clients follow the rel="next" URL to retrieve subsequent records until no further link is supplied.

A router or Layer 3 switch performs inter-subnet routing, forwarding packets between the 192.168.1.0/24 and 192.168.2.0/24 broadcast domains. Since these are distinct IP subnets, Layer 2 switching alone cannot bridge them; a Layer 3 device is required to satisfy the cross-subnet communication constraint.

The `event syslog pattern` trigger matches syslog messages against a regular expression, firing the applet when the specified pattern appears in the device log. This directly satisfies the stem's requirement to react to a specific syslog message, unlike timer, interface, or SNMP-based triggers.

Reading credentials from environment variables keeps secrets out of the codebase entirely. The script can access them at runtime without any sensitive values being stored in Git. This complements .gitignore by removing the need to commit credentials at all, satisfying the team's requirement to protect sensitive information.

The USER instruction sets the user name or UID that subsequent RUN, CMD, and ENTRYPOINT instructions run as. Placing USER appuser after creating the user ensures the container process starts without root privileges, which reduces the impact of a compromise and satisfies the requirement.

RESTCONF uses the YANG-derived media type application/yang-data+json to signal JSON-encoded YANG data in the request body. Setting it as Content-Type tells the device how to parse the payload, satisfying the stem's requirement to indicate YANG data in JSON format.

The Meraki Dashboard API authenticates requests with a dedicated header named X-Cisco-Meraki-API-Key carrying the organization's key. When that key is missing, revoked, or malformed, the dashboard rejects the call with a 401 Unauthorized status. This matches the scenario's requirement to read the key from an environment variable and place it in the correct header.

The -I option sends a HEAD request, so the server returns headers and status without a response body. This matches the goal of seeing only the status code and headers. It is the standard curl way to inspect metadata such as content type, cache directives, or rate-limit fields without downloading the full representation.

A Link header carrying rel="next" with an opaque URL is cursor-based pagination: the server dictates the next page location rather than the client computing offsets. This satisfies the scenario's identification of the pagination style used by the DNA Center issues endpoint.

NETCONF supports a candidate datastore where edits are staged, a validate operation that checks the candidate against the device's YANG models, and a commit that applies it atomically. If validation fails, the candidate can be discarded without touching the running configuration. This is exactly the model-driven, transactional workflow the requirement describes.

The Retry-After header tells the client exactly how many seconds to wait before retrying, so parsing it respects the server's advertised rate-limit window rather than guessing. This directly satisfies the scenario's need to handle 429 responses without breaching the API's throttling policy.

A range that permits newer 2.x releases while excluding 3.0 lets the consuming team install its required minor version and still blocks a breaking major upgrade. This resolves the resolver conflict without abandoning protection against incompatible changes, which is exactly the balance the scenario demands.

DAST probes the running application from the outside, exercising live endpoints to expose injection, authentication and configuration flaws that static review cannot reach. It satisfies the stem's requirement for pipeline security by catching runtime vulnerabilities before deployment, complementing SAST and dependency scanning within the CI/CD stages.