Free 300-535 Practice Test

The configuration snippet is for a Path Computation Element (PCE) on a Cisco IOS XR device, specifically for setting up high availability (HA). The command state-sync-ipv4 address 192.168.1.1 is used to define the IPv4 address of the peer PCE with which the local PCE will synchronize its state database. This synchronization is critical for a stateful PCE HA pair, ensuring that the standby PCE has an up-to-date copy of the Label Switched Path (LSP) database and can take over seamlessly if the active PCE fails.

A. The local PCEP listening address is not configured with this command. This command is for inter-PCE state synchronization, not PCC-PCE communication.
B. This command configures the address of the remote peer for synchronization, not the local device's address.
C. The destination address for PCEP is the PCE's address, but this specific configuration is for state synchronization between two peer PCEs, not for PCEP sessions.

1. Cisco IOS XR Segment Routing Configuration Guide, Release 7.3.x: In the "Configure Path Computation Element" chapter, under the "PCE High Availability" section, the state-sync-ipv4 address command is detailed. The guide states, "To configure the address of the peer PCE for state synchronization, use the state-sync-ipv4 address command in PCE configuration mode." This confirms the address belongs to the remote peer. (See section: PCE High Availability).

2. Cisco IOS XR Interface and Hardware Component Configuration Guide, Release 7.5.x: While discussing high availability concepts, the documentation implicitly supports that state synchronization occurs between peer devices. The configuration for PCE HA specifically uses the peer's address to establish this link. (See chapter: Implementing High Availability, section: Stateful Switchover (SSO)).

The Cisco Elastic Services Controller (ESC) Core Engine is the central component responsible for the lifecycle management of Virtual Network Functions (VNFs). It acts as the brain of the ESC, orchestrating complex operations. Its primary functions include managing transactions to ensure atomicity, validating requests against defined data models, enforcing policies, executing workflows for VNF deployment and scaling, maintaining VNF state machines, and handling rollback procedures in case of failures. This centralizes the logic for all VNF management tasks within the ESC architecture.

A. This statement describes the Northbound (NB) API component of Cisco ESC, which provides the interface for external systems like orchestrators, not the core engine itself.
B. This describes a deployment model for the entire Cisco ESC system to ensure service continuity, not the specific functional role of the core engine component.
C. This function is performed by the monitoring agent or monitoring component within Cisco ESC, which gathers health and KPI data, not the core engine.

1. Cisco Systems, "Cisco Elastic Services Controller User Guide, Release 5.2".

Section: Chapter: "Overview", Section: "Cisco ESC Architecture"

Content: This section explicitly states, "The ESC core engine is the primary component that manages transactions, validations, policies, workflows, VNF state machines, and rollbacks." This directly supports answer D. The same section also describes the other components, confirming that option A refers to the Northbound APIs and option C refers to the Monitoring Agent.

2. Cisco Systems, "Cisco Elastic Services Controller Install and Upgrade Guide, Release 5.2".

Section: Chapter: "High Availability for Cisco ESC", Section: "Overview of High Availability"

Content: This chapter details the high availability and cluster mode configurations. It describes this as a system-level deployment feature for redundancy, which confirms that option B is a characteristic of the overall ESC deployment, not the specific function of the core engine component.

The operation is the standard NETCONF Remote Procedure Call (RPC) used to request the graceful termination of a NETCONF session. According to the IETF standard governing NETCONF (RFC 6241), when a server receives a request, it must release any locks held by that session and reclaim all other resources associated with it before closing the underlying transport connection. This ensures a clean and orderly teardown of the management session, preventing orphaned locks or resource leaks on the network device.

A. : This is not a defined standard operation within the NETCONF protocol framework.
B. : This is not a standard NETCONF RPC. NETCONF operates on sessions and datastores, not "activities".
D. : This is not a NETCONF protocol operation. It appears to be a command related to device application management, not session control.

1. IETF RFC 6241, Network Configuration Protocol (NETCONF):

Section 5.4, "Closing a Session": "A NETCONF client can terminate a NETCONF session by sending a RPC to the server... The server will release any locks and resources associated with the session and close the connection." (Page 23)

2. Cisco IOS XE Programmability Configuration Guide, Cisco IOS XE Gibraltar 16.12.x:

Chapter: NETCONF Protocol Operations, Section: NETCONF Session Management: "The operation requests the graceful termination of a NETCONF session. When a NETCONF server receives a request, the server releases any locks held by the session..."

3. Cisco Crosswork Network Controller 4.2.0 NETCONF and YANG API Guide:

Chapter: NETCONF Protocol, Section: NETCONF Operations: This guide lists as a base protocol operation for terminating a session, consistent with the RFC standard. It states, "The operation requests the graceful termination of a NETCONF session."

Assume the code defines b = 22 and d = 44, and swap1 is written as

def swap1(x, y): x, y = y, x return (x, y)

Calling swap1 therefore returns the two arguments in reverse order. To obtain the tuple (44, 22), we must give swap1 the values in the opposite order—first 22 (b), then 44 (d). print(swap1(b, d)) consequently prints (44, 22).

A. swap1(d, b) returns (22, 44) because the arguments are reversed inside the function.
B. swap2(a, b) acts on different variables; even if swap2 swaps, it involves a and b, not d.
D. swap2(22, 44) passes immutable ints; an in-place swap (likely using list indexing) cannot occur, raising an error.

1. Python Software Foundation. “The Python Language Reference – Assignment Statements,” Python 3.11 docs, §6.2.1 (explains tuple-unpacking swap).

https://docs.python.org/3/reference/simplestmts.html#assignment-statements

2. Python Software Foundation. “Data Model – Immutable Sequence Types,” Python 3.11 docs, §4.6 (ints are immutable, making in-place swap impossible).

https://docs.python.org/3/reference/datamodel.html#immutable-sequence-types

In RESTCONF the URI …/extended=BLOCKBAD identifies one list instance; a PUT must therefore supply a complete replacement for that list. The body must start with the top-level container “Cisco-IOS-XE-acl:extended”, include the key leaf “name”: "BLOCKBAD”, and then the ordered “access-list-seq-rule” array that holds sequence numbers 10 and 20 with the appropriate permit/deny structures.
Option D is the only body that:
• begins with “Cisco-IOS-XE-acl:extended”,
• carries the key “name”: "BLOCKBAD",
• provides both sequence rules exactly matching “permit ip any host 192.168.20.1” and “deny ip any any”, thus yielding the desired running-config.

A – Omits the outer “Cisco-IOS-XE-acl:extended” container; body is therefore not valid against the ACL YANG model. B – Uses PATCH style (only rule fragment) and lacks the mandatory key “name”; a PUT would fail schema-validation. C – Places “access-list-seq-rule” at top level and misses the namespace prefix, violating the YANG hierarchy. D – (chosen).

1. Cisco IOS XE Programmability Configuration Guide, Gibraltar 16.12 – section “Using RESTCONF to Configure Access Control Lists”, Example 8-4 (PUT …/extended=ACL1) pp. 126-128.

2. Cisco-IOS-XE-acl YANG module (16.12) – list extended, leaves name & access-list-seq-rule, lines 55-94.

3. IETF RFC 8040, sec. 4.5.3 – PUT replaces the target resource in its entirety.

In a template-based NSO service, the skeleton template resolves run-time variables that are defined in the service YANG. The standard way to associate a target network element with the service is to include a “device” leaf (or leaf-list) in the service YANG and reference it in the template as ${device}. Consequently, to enter (bind) a device into the model, the engineer must edit the device instance so that the “device” variable from the service YANG is populated. Other variables (for example “acllab”) are unrelated and do not place the device inside the YANG service tree.

A. “acllab” is not the canonical device key in the service YANG; editing it will not register the device under the service instance.
B. Deploying a VLAN to every device does not add a single device entry to the service’s YANG structure.
C. A leaf-list of devices could exist, but creating the service instance is different from modifying the individual device node in the model.

1. Cisco Systems, “NSO Service Modeling Guide 6.0”, Chapter 3: Using Templates, Example 3-2 – Variable ${device} in skeleton template (pp. 33-36).

2. Cisco Systems, “Network Services Orchestrator 6.0 – Developer Guide”, Section 4.2 “Defining service variables” – requirement for a ‘device’ leaf to bind a device (pp. 52-54).

3. Stanford University EE384X Course Notes, “YANG Modeling with NSO”, slide set 2, slide 17 – mapping the ‘device’ leaf to the template variable.

The commit dry-run command in the Cisco NSO CLI is used to simulate the commit process. It calculates the delta between the current running configuration and the new configuration in the transaction, and then determines the specific commands that would be sent to the network devices to enact these changes. The outformat native option formats this output into the device's native command-line syntax (e.g., Cisco IOS-XE or Junos commands). This allows an operator to inspect the exact configuration changes that will be pushed to each device before actually applying them, fulfilling the requirement of the question.

A. show service impact: This is not a valid Cisco NSO command. While you can view service data, this specific syntax does not exist for previewing device configuration changes.
C. pseudo-commit: This is not a valid Cisco NSO command. The correct term for simulating a commit without applying changes is dry-run.
D. show dry-run output: This is not a valid Cisco NSO command. The dry-run functionality is an option appended to the commit command, not a standalone show command. ---

1. Cisco NSO Administration Guide, 6.0: In the "The Commit Command" chapter, the dry-run option is detailed. It states, "The dry-run option is used to see what NSO would send to the devices without actually sending it." The guide further explains the outformat option, specifying that native "displays the configuration in the native format of the device."

Reference: Cisco NSO 6.0 Administration Guide, Chapter: The Commit Command, Section: The dry-run Option.

2. Cisco NSO CLI Command Reference, 6.0: The reference guide for the NSO CLI explicitly documents the commit command and its parameters. It lists dry-run as a primary option and outformat as a sub-option for dry-run.

Reference: Cisco NSO 6.0 CLI Command Reference, Chapter: Configuration Mode Commands, Section: commit.

3. Cisco DevNet NSO Basics Learning Lab: The "Committing changes to the network" module demonstrates the use of commit dry-run. The lab instructions state: "To see what NSO would send to the devices without actually sending anything, use the commit dry-run command... To see the native device commands that would be sent, add the outformat native option."

Reference: Cisco DevNet Learning Labs, NSO Basics, Module: Committing changes to the network, Step 2: Dry Run.

The script receives a 405 Method Not Allowed error because it attempts to invoke a Cisco NSO action using the HTTP GET method. According to the RESTCONF protocol standard (RFC 8040), YANG RPCs and actions must be invoked using the HTTP POST method. The specific NSO action to retrieve SSH host keys from a device is named fetch-host-keys, as defined in the tailf-ncs.yang model. Therefore, the correct code must use requests.post with the URI pointing to the .../ssh/fetch-host-keys operation to successfully execute the task.

A. The PUT method is incorrect for invoking a RESTCONF action. PUT is used to create or replace a data resource, not to execute an operation.
C. The action name request-host-keys is incorrect. The standard NSO action defined in the tailf-ncs.yang model is fetch-host-keys.
D. This option is incorrect for two reasons: it uses the wrong HTTP method (PUT) and the wrong action name (request-host-keys).

1. Cisco NSO Programmability Guide, 6.1, RESTCONF Chapter: In the section "Operations (RPCs and Actions)", the documentation states, "To invoke an RPC or action, the client sends a POST request to the resource that represents the RPC or action." This confirms POST is the correct method.

2. IETF RFC 8040, "RESTCONF Protocol", Section 4.4: This standard specifies the protocol mechanics for RESTCONF. It states, "The client invokes an operation by sending a POST method request to the target resource." This confirms that GET is not allowed and POST is required.

3. Cisco NSO YANG API Reference Documentation: The tailf-ncs.yang model, which is fundamental to NSO's device management, defines the action for retrieving SSH keys as fetch-host-keys within the /devices/device/ssh container. The RESTCONF path is derived directly from this YANG model structure.

Network Element Drivers (NEDs): Serve as the abstraction layer that allows NSO to communicate with physical or virtual devices using their native protocols (CLI, REST, NETCONF, etc.) without the core needing to know specific device syntax.

Configuration Database (CDB): A hierarchical database that stores the complete network configuration (the "Source of Truth"), including device configurations and service operational data, often in-memory for speed.

Device Manager: Responsible for the management of the devices themselves, including tasks like connectivity management and synchronization (e.g., sync-from to pull running configurations).

Package Manager: Handles the administration of NSO packages, which can contain NEDs, service models, and other extensions, allowing them to be loaded or updated.

Service Manager: Implements the FASTMAP algorithm to manage the lifecycle of services, mapping high-level service intent to low-level device configurations and supporting arbitrary modifications (create, modify, delete) automatically.

Cisco Network Services Orchestrator (NSO) Administration Guide, Chapter: NSO Architecture, Section: The NSO Components.

Confirms: "The Device Manager manages the devices in the network... functions include... synchronization of configuration."

Confirms: "The NEDs are responsible for talking to the devices."

Cisco Network Services Orchestrator System Architecture, White Paper.

Confirms: "CDB... stores the complete network configuration."

Confirms: "Service Manager... FASTMAP... allows for arbitrary modifications."

Cisco NSO User Guide, Section: Package Management.

Confirms: The role of the Package Manager in handling NED and service packages.

To create a service template in Cisco NSO, the device configuration must be represented in XML format. The NSO CLI command show running-config is used to view the configuration of a managed device as it exists in NSO's Configuration Database (CDB). The | display xml modifier formats this output into the required XML structure. This generated XML can either be displayed directly in the CLI (Option E) to be copied manually or saved directly to a file using the | save pipe (Option B). Both commands effectively generate the necessary template content from a live device configuration.

A. display template.xml is not a valid NSO CLI modifier. The correct modifier to generate the XML output is display xml.
C. The request command is used to execute actions or RPCs, not to display configuration from the CDB. The correct command is show.
D. This command displays the configuration in a native or tree format, not the XML format required for an NSO service template.

1. Cisco NSO 6.0 Developing and Operating Services Guide, Chapter: Creating a Service, Section: Creating a Template-Based Service: This guide details the workflow for creating a service from a template. It explicitly demonstrates using the show running-config devices device config ... | display xml command to obtain the XML configuration snippet that forms the basis of the service template. This supports option E.

2. Cisco NSO 6.0 CLI Guide, Chapter: The CLI, Section: The Pipe Character: This section explains the usage of the pipe | character to process command output. It lists save as a valid command to save the preceding output to a file, which validates the command structure used in option B.

3. Cisco NSO 6.0 CLI Guide, Chapter: The CLI, Section: Displaying Data in Different Formats: This section documents the display modifier and lists xml as a valid format option for commands like show running-config. This confirms the core syntax used in both correct options (B and E) and invalidates the syntax in option A.