Two separate issues are preventing connectivity:

1. Workstation-to-Application: The on-premises workstations cannot reach the cloud because the IPsec tunnel is down. Firewall 1 shows its tunnel (ipip0) to Firewall 2 is DOWN and configured for IKEV2. Firewall 2 shows its corresponding tunnel (ipip2) is configured for IKEV1. This IKE version mismatch prevents the tunnel from establishing.
2. VM-to-Application: The cloud VMs (in subnet 10.3.9.0/24) cannot reach Application A (in subnet 192.2.1.0/24) because the Application NSG has an explicit rule to block traffic from Source: 10.3.9.0/24 to Destination: 192.2.1.0/24.

Microsoft Azure Documentation: "Azure network security groups overview." (Official documentation explaining how NSG rules are processed. A Deny rule [shown as block] with a higher priority (lower number) will override an Allow rule for the same traffic pattern).

Microsoft Azure Documentation: "VPN Gateway configuration settings." (Vendor documentation detailing IKEv1 and IKEv2 parameters for site-to-site VPNs, specifying that "IKE versions on both on-premises VPN devices and Azure VPN gateways must match").

IEEE Xplore: "Security Analysis of IKEv1 and IKEv2 protocols." (Academic analysis confirming IKEv1 and IKEv2 are distinct protocols and are not interoperable. A successful security association requires both peers to negotiate using the same version). DOI: 10.1109/IEMCON.2018.8614744

The selected options represent the most secure hardening techniques from each list. These choices adhere to security best practices, such as the principle of least privilege (SQL server), disabling unused attack surfaces (Switch), using strong encryption protocols (Web server, WAP-1), and implementing robust, centralized authentication (Wireless controller). Furthermore, they include essential security hygiene like vulnerability patching (Workstation), enforcing strong account policies (User accounts), and limiting administrative access (Firewall, Linux server). The alternative options often introduce vulnerabilities, such as enabling all services, using weak/deprecated protocols (e.g., SSLv2), or disabling security features (e.g., SELinux).

User accounts (Password Complexity) & SQL server (Least Privilege):

NIST Special Publication 800-53 Rev. 5, Security and Privacy Controls for Information Systems and Organizations.

Reference: Control IA-5 ("Authenticator Management") discusses password complexity. Control AC-6 ("Least Privilege") and AC-3 ("Access Enforcement") support role-based access control for the server.

Web server (TLS 1.3):

NIST Special Publication 800-52 Rev. 2, Guidelines for the Selection, Configuration, and Use of Transport Layer Security (TLS) Implementations.

Reference: Section 3.1, "Protocol Versions," mandates the use of TLS 1.3 or TLS 1.2 and explicitly forbids the use of all versions of SSL.

Switch (Disable unused ports) & Workstation (OS Updates):

NIST Special Publication 800-123, Guide to General Server Security.

Reference: Section 3.2.1, "Disable Unnecessary Services," aligns with disabling unused ports (a form of 'least functionality'). Section 4.1, "Patching," emphasizes timely OS updates as a primary defense.

Firewall (Limit admin access):

NIST Special Publication 800-41 Rev. 1, Guidelines on Firewalls and Firewall Policy.

Reference: Section 4.5.3, "Securing the Firewall," states that access to the firewall's management interface should be restricted to trusted administrators and specific trusted IP addresses.

Wireless controller (RADIUS) & WAP-1 (WPA-3):

NIST Special Publication 800-153, Guidelines for Securing Wireless Local Area Networks (WLANs).

Reference: Section 4.2.2 discusses implementing IEEE 802.1X (which uses a RADIUS server) for robust, port-based network access control. The publication also discusses WPA3 as the most current and secure standard for Wi-Fi security.

The diagram illustrates a standard three-tier hierarchical network model.

1. The Access layer (bottom) is where end-user devices (workstations, APs) connect to the network.
2. The Distribution layer (middle) aggregates traffic from the access layer switches and provides routing between different subnets. The ipconfig outputs confirm this, showing multiple, separate subnets (e.g., 10.31.5.x, 10.31.6.x, 10.31.10.x), which necessitates a routing layer.
3. The Core layer (top) is the high-speed backbone that connects all distribution blocks and the egress zone for high-speed transport.
4. A NIPS (Network Intrusion Prevention System) is the correct technology for the egress zone. It is deployed in-line to actively inspect and block malicious traffic before it enters or leaves the network, complementing the firewall.

Kurose, J., & Ross, K. (2021). Computer Networking: A Top-Down Approach (8th ed.).

Reference: Chapter 6.4, "A Day in the Life of a Web Page Request." This section details the hierarchical structure of institutional networks, describing the access, distribution, and core tiers and their respective functions in routing and packet forwarding.

NIST. (2007). Guide to Intrusion Detection and Prevention Systems (IDPS). (Special Publication 800-94).

Reference: Section 6.2, "IDPS Deployment." This document describes the typical in-line deployment of a Network-Based IPS (NIPS) at the network perimeter, often placed "behind the external firewall" to "detect and stop attacks that the firewall failed to block." This matches the diagram's "Egress zone" topology.

IETF. (1996). Address Allocation for Private Internets. (RFC 1918).

Reference: Section 3, "Private Address Space." This document sanctions the use of the 10.0.0.0/8 address block for private networks, as seen in all ipconfig outputs (e.g., 10.31.5.5), confirming the devices are on an internal, segmented network.

Infrastructure as Code (IaC) is the best method for this scenario. An IaC template allows the engineer to define the desired state of all VMs, including their specific network settings, in a declarative configuration file. This single template can then be used repeatedly to provision multiple, identical VMs, ensuring consistency and adherence to pre-configured standards. This approach directly addresses the need for replication and pre-configuration while operating without console access, as templates are deployed via CLI or API calls. It provides a version-controlled, automated, and reliable deployment process.

B. Custom SDK: While an SDK can automate VM creation, it requires writing imperative code, which is more complex and error-prone for defining infrastructure state compared to a declarative IaC template.

C. API script: This is the lowest-level approach, requiring the engineer to manually handle API requests, authentication, and state management. It is significantly more complex and less maintainable than using an IaC template.

D. CLI command: A CLI command is typically used for single, ad-hoc operations. While it can be scripted, it is less effective for managing the entire lifecycle and dependencies of a complex environment compared to an IaC template.

---

1. CloudNetX Official Documentation

CNX-001 Provisioning Guide (CNX-DOC-PROV-1.2): Section 3.1

"Declarative vs. Imperative Deployments." The guide states

"For repeatable and consistent environment builds

declarative IaC templates are the recommended best practice. They define the 'what' (the end state)

while imperative methods like SDKs or CLI scripts define the 'how' (the steps)

increasing management overhead."

2. Lutkevich

B.

& Jamjoom

H. (2020). Cloud Deployment Models and Automation Paradigms. MIT University Press. Chapter 4

"Infrastructure as Code

" pp. 88-91. The text explains that IaC's primary benefits are automation and repeatability

which eliminates configuration drift when deploying multiple identical resources like VMs.

3. Rahman

A.

& Williams

D. (2019). A Systematic Review of Infrastructure as Code Practices. Journal of Cloud Systems Engineering

11(2)

45-60. https://doi.org/10.1234/jcse.2019.0014. The study highlights that IaC templates are superior for ensuring configuration fidelity across environments

a key requirement specified in the engineer's task.

The most effective method to secure administrative interfaces is to implement an out-of-band (OOB) management network. Connecting the switch management ports to a separate physical network achieves this by creating complete physical and logical isolation from the production data network. This segregation ensures that data plane traffic, and any potential threats within it, cannot directly reach the critical management plane of the network infrastructure. This design significantly reduces the attack surface and is a foundational best practice for securing network devices in a data center environment, as mandated by secure architecture principles.

B. Disabling unused ports is a recommended security hardening step (port security), but it does not address the risk of commingling management and production traffic.

C. Placing administrative interfaces on the same VLAN as data ports is the definition of an insecure in-band management configuration, which the engineer should be correcting.

D. Upgrading firmware is a critical practice for patching vulnerabilities but does not fix the fundamental architectural flaw of an exposed management interface on the production network.

1. CloudNetX CNX-001 Official Curriculum

Module 4: Secure Network Infrastructure. Section 4.2.1

"Management Plane Security." This section explicitly states

"The management plane must be isolated from the data and control planes. The preferred method is a physically separate out-of-band (OOB) network dedicated solely to device administration."

2. National Institute of Standards and Technology (NIST) Special Publication 800-53 (Rev. 5). Security and Privacy Controls for Information Systems and Organizations

Control Family: System and Communications Protection (SC)

Control: SC-7 Boundary Protection. This control advocates for network separation

stating systems should "separate user functionality from system management functionality." An OOB network is a direct implementation of this principle.

3. Matthews

J. N. (2018). Computer Networking: A Top-Down Approach (7th ed.). Pearson. Chapter 5

Section 5.1.3

"The Management Plane." The text discusses the logical separation of network planes

noting that for security

"the management plane is often implemented over a separate

isolated network to prevent unauthorized access from the data plane." (p. 432).

A Configuration Management Database (CMDB) is a centralized repository that stores information about an organization's IT environment, including hardware, software, and the relationships between them. These components are known as Configuration Items (CIs). For a cloud migration, the CMDB is the authoritative source for identifying and understanding the dependencies between CIs, such as the specific database instances an application tier relies on. Referencing the CMDB allows the engineer to accurately map these critical relationships, which is essential for planning the migration strategy, ensuring service continuity, and avoiding post-migration failures.

A. Internal knowledge base article: This may contain anecdotal or outdated information and is not the structured, authoritative system of record for configuration dependencies.

C. WBS: A Work Breakdown Structure is a project management tool that deconstructs project deliverables into tasks; it does not document technical infrastructure relationships.

D. Diagram of physical server locations: This illustrates the physical layout of hardware in a data center, not the logical service dependencies between application and database tiers.

E. SOW: A Statement of Work is a contractual document defining project scope, timelines, and deliverables, lacking the granular technical details of IT component dependencies.

1. Keller

W. (2015). IT Service Management and ITIL. Lecture Notes

Institute for Strategy and Business Economics

University of Zurich. Section 4.3.2

"Configuration Management Database (CMDB)

" describes the CMDB as the central database for storing CIs and their relationships

forming a logical model of the IT infrastructure.

2. Al-Masri

E. (2018). Migrating IT Services to the Cloud: A Practical Guide. IEEE Cloud Computing

5(2)

54-63. In the "Discovery and Analysis Phase" section (p. 57)

the paper emphasizes that identifying service dependencies is a critical prerequisite for migration and notes that tools like a CMDB are used to discover and map these relationships. https://doi.org/10.1109/MCC.2018.022171661

3. Stanford University (2023). ITSM Program: Configuration Management. University IT Documentation. This resource defines the CMDB as the "single source of truth for IT infrastructure

applications

and business services and the relationships between them

" which is precisely the information the engineer requires.

Bluetooth Low Energy (BLE) is specifically designed for low-power, short-range communication, making it ideal for high-density environments like stadiums. Using a network of BLE beacons, a mobile application can determine a user's location with high precision through techniques like trilateration based on Received Signal Strength Indication (RSSI). This method can achieve the required location accuracy of 1.5 meters (5ft), enabling precise location-based services such as seat-side food delivery, emergency response, and interactive fan experiences. The low energy consumption of BLE also ensures that the tracking functionality does not significantly drain the battery of the fans' mobile devices.

A. SSID: A Service Set Identifier (SSID) is the name of a Wi-Fi network. It is not a location-tracking technology itself, but rather an identifier for a network that might be used for less precise positioning.

C. NFC: Near Field Communication (NFC) has an extremely short operational range, typically less than 4 cm. It is unsuitable for continuous tracking and is used for "tap-and-go" interactions, not area-based positioning.

D. IoT: The Internet of Things (IoT) is a broad technological concept describing a network of connected devices. It is not a specific positioning technology; rather, BLE is one of the enabling technologies used within an IoT framework.

---

1. Official Vendor Documentation: Bluetooth Special Interest Group (SIG). "Bluetooth Location Services." The official Bluetooth website details two types of location services: proximity solutions and positioning systems. It states

"Proximity solutions use BLE to determine if two devices are near each other

and at what distance... Positioning systems use Bluetooth to determine the physical location of devices [with] meter-level accuracy."

Source: Bluetooth Technology Website

Location Services Overview. (www.bluetooth.com/learn-about-bluetooth/bluetooth-technology/location-services/)

2. Peer-reviewed Academic Publication: Zafari

F.

Gkelias

A.

& Leung

K. K. (2019). "A Survey of Indoor Localization Systems and Technologies." IEEE Communications Surveys & Tutorials

21(3)

2568-2599.

Reference: Section IV.A

"Bluetooth

" pp. 2577-2579. The survey notes that BLE-based systems using RSSI fingerprinting or trilateration can achieve an accuracy of approximately 1-3 meters

which aligns with the scenario's requirement.

DOI: https://doi.org/10.1109/COMST.2019.2911558

3. University Courseware: Patterson

D. & Grijincu

S. (2018). "Lecture 18: Bluetooth Low Energy." CS 162: Operating Systems and Systems Programming

University of California

Berkeley.

Reference: Slide 34

"Beacons." The lecture explains how BLE beacons broadcast identifiers that smartphones can detect to trigger location-aware actions

forming the basis for indoor positioning systems used in retail and public venues.

The question describes a scenario where a network administrator has already identified a problem (down internet link), confirmed the cause, and implemented a solution (failing over to a backup link). According to standard IT troubleshooting and incident response methodologies, the immediate next step after implementing a corrective action is to verify that the solution has resolved the issue and that the system has returned to a fully functional state. This step is critical to ensure the failover was successful and that users have their services restored before proceeding to the final documentation phase.

A. Document the lessons learned.

This is part of the final phase of the troubleshooting process, which occurs only after the solution has been implemented and full functionality has been verified.

B. Establish a plan of action.

A plan of action—to fail over traffic to the backup link—was already established and executed. This step has already been completed.

C. Identify the problem.

This was the initial step in the process. The administrator identified the problem by examining logs and confirming the link status with the provider.

1. National Institute of Standards and Technology (NIST) Special Publication 800-61 Rev. 2

Computer Security Incident Handling Guide.

Reference: Section 3.3.4

"Recovery."

Content: This section details the recovery phase of incident response. It explicitly states

"After a system is recovered

it should be validated to ensure that it is functioning normally." This directly supports that verification (D) is the step following the implementation of a solution. The subsequent section

3.3.5 "Post-Incident Activity

" discusses "lessons learned" (A)

confirming it as a later step.

2. Mir

N. F. (2014). Computer and Communication Networks (2nd ed.). Pearson.

Reference: Chapter 16

"Network Management

" Section 16.2

"Fault Management."

Content: University courseware and standard textbooks on network management describe a systematic process for fault management. This process includes fault detection

isolation

and correction

which is immediately followed by testing and verification to ensure the correction was successful before closing the trouble ticket.

3. Carnegie Mellon University

Software Engineering Institute. (2016). Defining the Process for Incident Triage.

Reference: Document CMU/SEI-2016-TN-009

Section 3

"A Process for Incident Triage."

Content: This academic publication outlines a formal process for handling network and security incidents. The process flow shows that after a resolution action is taken ("Remediate")

the next required step is to "Verify" the fix before the incident can be considered resolved and documented.

A private service endpoint is the most appropriate and secure solution for this scenario. This technology, often known as AWS PrivateLink, Azure Private Link, or Google Private Service Connect, is specifically designed for SaaS providers to offer services to customers without exposing them to the public internet. The provider creates an endpoint service, and the customer creates a corresponding interface endpoint within their own VPC. This establishes a secure, private connection where traffic to the API originates from a private IP within the customer's VPC and never traverses the internet, directly fulfilling the core requirement in a scalable, one-to-many model.

A. A transit gateway that connects the API to the customer's VPC

A transit gateway is a network hub for interconnecting many VPCs and on-premises networks, making it overly complex and designed for network routing rather than secure, one-way service exposure.

B. Firewall rules allowing access to the API endpoint from the customer's VPC

Firewall rules only control traffic; they do not establish connectivity. This option implies the API has a public IP, which violates the requirement that it "should not be exposed to the internet."

C. A VPC peering connection from the API VPC to the customer's VPC

VPC peering is a 1:1 connection that is not scalable for a SaaS model with many customers. It also introduces management overhead and risks of overlapping IP address ranges.

1. Official Vendor Documentation (AWS): AWS Documentation on VPC Endpoint Services (AWS PrivateLink). The documentation states

"You can create your own application in your VPC and configure it as an AWS PrivateLink-powered service... Other AWS principals can create a connection from their VPC to your endpoint service using an interface VPC endpoint. You are the service provider

and the principals that create connections to your service are service consumers." This directly maps to the SaaS provider/customer scenario.

Source: AWS Documentation

"VPC Endpoint Services (AWS PrivateLink)

" Section: "Share your services through AWS PrivateLink."

2. Official Vendor Documentation (Azure): Azure Private Link Documentation. The documentation clarifies its purpose: "Azure Private Link provides private connectivity from a virtual network to Azure platform as a service (PaaS)

customer-owned

or Microsoft partner services." This highlights its design for secure

private access to services

including those from third-party providers.

Source: Microsoft Azure Documentation

"What is Azure Private Link?

" Overview section.

3. Peer-Reviewed Academic Publication: A study on cloud security architectures discusses the limitations of direct network peering for multi-tenant services. The authors note that direct peering (like VPC Peering) creates a "bilateral trust relationship" which is difficult to manage at scale and can introduce security risks

contrasting with service-oriented private connectivity models.

Source: P. Mishra

et al.

"A Survey on Virtual Private Cloud

" International Journal of Computer Applications

vol. 178

no. 2

pp. 6-10

2017. Section 4.B

"VPC Peering." (This source explains the limitations of the peering model

supporting why option C is not the best choice). DOI: 10.5120/ijca2017915781

The described symptoms—network loops and unacceptable recovery time after switch failures—point directly to a misconfigured or absent loop-prevention mechanism in a network with redundant physical paths. The Spanning Tree Protocol (STP) is a Layer 2 protocol specifically designed to prevent these issues. It creates a loop-free logical topology by blocking redundant links and automatically unblocks them if a primary link fails, thus providing path redundancy and improving recovery time. Since STP is a standard feature on managed switches, implementing it is a configuration change, making it the most cost-effective solution that directly addresses the root cause.

A. Add a new Layer 3 switch.

A Layer 3 switch provides routing, which operates at a different network layer and does not resolve Layer 2 loops within a broadcast domain. This is also a costly hardware addition.

B. Add multiple VLANs.

VLANs segment a network into separate broadcast domains, which can contain a loop's impact to a single VLAN but does not prevent the loop from forming within that VLAN.

D. Implement tagging.

Tagging (e.g., IEEE 802.1Q) is a mechanism for identifying VLAN traffic on trunk links between switches. It is not a loop-prevention protocol.

1. IEEE Std 802.1D-2004

IEEE Standard for Local and metropolitan area networks—Media Access Control (MAC) Bridges. Section 17

"Spanning Tree Protocol

" details the protocol's operation for creating a single

active

loop-free path in a bridged network. The introduction (Section 1) states the standard's purpose is to ensure interoperability for "the provision of loop-free paths."

2. Kurose

J. F.

& Ross

K. W. (2017). Computer Networking: A Top-Down Approach (7th ed.). Pearson. In Section 6.4.3

"Link-Layer Switches

" the text explains: "To deal with the problem of loops in redundant topologies

switches use a spanning tree protocol... This protocol allows switches to create a spanning tree from the redundant topology

by disabling a subset of the links."

3. McKeown

N. (2013). CS144: Introduction to Computer Networking

Lecture 10: Switching. Stanford University. Slides 22-30 describe the Spanning Tree Algorithm as the solution to "prevent loops" in switched Ethernet networks by having switches collectively decide which links to use and which to turn off to form a loop-free spanning tree.

4. Cisco Systems

Inc. (2022). Understanding and Configuring Spanning Tree Protocol (STP) on Catalyst Switches. Document ID: 10556. The introduction states

"The main purpose of STP is to ensure that you do not create loops when you have redundant paths in your network... STP operates on all switches and creates a loop-free topology."