Understanding the Vulnerability:
Vulnerabilities in the router CPU can be exploited to cause performance degradation, unauthorized access, or other security issues.
Firmware Update:
Firmware Role: The firmware is low-level software that controls the hardware of a device. Updating the firmware can address vulnerabilities by providing patches and enhancements from the manufacturer.
Procedure: Download the latest firmware from the vendor's website, follow the manufacturer's instructions to apply the update, and verify that the update resolves the vulnerability.
Comparison with Other Options:
Replace the System Board: This is a costly and often unnecessary step if the issue can be resolved with a firmware update.
Patch the OS: Patching the OS is relevant for devices with a full operating system but not directly applicable to addressing a CPU vulnerability on a router.
Isolate the System: Temporarily isolating the system can mitigate immediate risk but does not resolve the underlying vulnerability.
Best Practice:
Regularly check for and apply firmware updates to ensure that network devices are protected against known vulnerabilities.
References:
CompTIA Network+ study materials on network security and device management.

The technician should inspect the client's firewall configuration. Since only one specific user is unable to access the server while other users can access it successfully, the issue is most likely isolated to that user's device, account, local configuration, or local security settings. After switch and router logs show no network infrastructure issue, the next logical step is to examine the affected client.
The CompTIA Network+ N10-009 troubleshooting methodology emphasizes identifying the scope of the problem, testing the most likely causes, and isolating whether the issue is client-side, server-side, or network- side. A local firewall could block outbound connections to the server, block a required application, restrict ports, or apply a profile that prevents communication.
Updating network firmware is not an appropriate next step because there is no evidence of a widespread infrastructure problem. Checking the server's DNS configuration is unlikely because other users can access the same server. Checking the server's event logs may be useful later, but the scenario points first to the single affected client. Therefore, inspecting the client's firewall configuration is the best next troubleshooting step.

802.1Q tagging, also known as VLAN tagging, is used to identify VLANs on a trunk link between switches.
This allows the switches to transfer data for multiple VLANs (or networks) over a single physical connection.
This method ensures that traffic from different VLANs is properly separated and managed across the network.
References: CompTIA Network+ study materials.

The correct answer is A. TACACS+. This protocol is commonly used for authentication, authorization, and accounting (AAA) when administrators need to access network infrastructure devices such as routers, switches, and firewalls. The key part of the question is not just authentication, but also logging capabilities.
TACACS+ supports accounting functions, which means it can record administrative actions and login events.
That makes it especially useful when organizations want traceability for device access and configuration changes.
The other options do not fit as well. SAML is primarily used for federated identity and web-based authentication between identity providers and service providers. SSO is a general authentication convenience feature that allows one login to access multiple systems, but it does not itself provide detailed device-level accounting. MFA strengthens authentication by requiring multiple factors, but it is not the protocol best known for centralized access control and activity logging on network devices.
For Network+ exam purposes, TACACS+ is strongly associated with administrative access to network equipment and with maintaining an audit trail of who accessed devices and what actions were performed.
Because the question asks for both simple authentication and logging, TACACS+ is the best match.

Security groups in cloud environments act as virtual firewalls for VM instances, controlling inbound and outbound traffic based on specified rules.
From Andrew Ramdayal's guide:
"Network security groups are used to control inbound and outbound traffic to cloud resources within a VPC.
They act as a virtual firewall for associated instances..."