When a network administrator observes CRC errors on a specific switchport associated with one user, the first troubleshooting step recommended is to replace the user's network cable. CRC errors are often indicative of physical layer issues such as noise, interference, or damaged cables. By replacing the network cable, the administrator can potentially resolve these errors without more drastic measures like replacing hardware components (NIC, switch, or uplink cables), which could be more costly and less effective as initial steps. This approach minimizes downtime and is a cost-effective first step in the troubleshooting process.

If the port is shut down, it means that the switch has disabled the port and is not sending or receiving any traffic on it. This would explain why the network interface's indicator lights are not blinking on either the computer or the switch, and why the user cannot access resources on the network. The port could be shut down manually by the network administrator, or automatically by the switch due to security or error conditions.
References
* Port shutdown is one of the common switch configuration options covered in Objective 2.3 of the CompTIA Network+ N10-008 certification exam1.
* Port shutdown can cause the network interface's indicator lights to stop blinking2.
* Port shutdown can prevent the user from accessing resources on the network3.
1: CompTIA Network+ Certification Exam Objectives, page 5 2: CompTIA Network+ N10-008: Switch not forwarding frames on trunked port3 3: Cable Management - N10-008 CompTIA Network+ : 1.3

Audit logs are records of the actions performed by users or processes on a system or network device. They can provide information about who made what changes, when, and why. Audit logs are essential for detecting and investigating security incidents, as well as for ensuring compliance with policies and regulations. Audit logs can help the network security engineer to identify the source of the unauthorized configuration changes to the boundary firewall, as well as the scope and impact of the changes.
References1 - Changes to Cyber Essentials requirements - April 2021 update2 - 8 Firewall Best Practices for Securing the Network3 - How to secure your network boundaries with a firewall

Explanation
BGP is a routing protocol that is used to exchange routing information between different autonomous systems (ASes) on the internet. An autonomous system is a network or group of networks that is under the same administrative control and uses a common routing protocol. By acquiring its own public IP prefixes and autonomous system number, a company can use BGP to advertise these prefixes to other ASes and establish its own internet connection. This would enable the company to have more control over its internet connection and potentially improve its connectivity.EIGRP (Enhanced Interior Gateway Routing Protocol) is a routing protocol used within a single autonomous system, so it would not be used to establish a connection to the internet. IPv6 is a version of the Internet Protocol (IP) used to identify devices on a network. It is not a routing protocol and would not be used to establish an internet connection.MPLS (Multi-Protocol Label Switching) is a networking technology that is used to route packets between different networks. It is not a routing protocol and would not be used to establish an internet connection.

Explanation
The IP address configured on the router interface is 196.26.4.1/26, which belongs to the IP range assigned by the ISP (196.26.4.0/26). However, this IP address is not valid for this interface because it is the network address of the subnet, which cannot be assigned to any host device. The network address is the first address of a subnet that identifies the subnet itself. The valid IP addresses for this subnet are from 196.26.4.1 to
196.26.4.62, excluding the network address (196.26.4.0) and the broadcast address (196.26.4.63). The router interface should be configured with a valid IP address within this range to restore Internet connectivity for all users. References:
https://partners.comptia.org/docs/default-source/resources/comptia-network-n10-008-exam-objectives-(2-0),
https://www.techopedia.com/definition/24136/network-address