A technician is setting up a surveillance system for a customer. The customer wants access to the system's web interface on the LAN via the system’s…

The question is flawed in its phrasing, but the most relevant concept is port mapping (or port forwarding). By default, a NAT router blocks all unsolicited incoming traffic from the internet. Port mapping is the feature used to create exceptions, allowing external traffic to reach a specific device on the LAN. To prevent external access, the technician must ensure no port mapping rule is configured for the surveillance system's IP address and web interface port. Therefore, managing the port mapping settings is the correct action.

B. Subnetting: This divides a network into smaller segments for organization or performance but does not inherently block internet access to a device.

C. Static IP: Assigning a static internal IP address makes a device easier to find on the LAN but does not control its accessibility from the internet.

D. Content filtering: This is used to block outbound traffic from the LAN to the internet (e.g., blocking websites), not for preventing inbound connections.

1. Cisco, "NAT: Local and Global Definitions," Cisco Press, Document ID: 13708. This document explains how Network Address Translation (NAT) and Port Address Translation (PAT) inherently block unsolicited inbound connections unless a static mapping (like port forwarding) is created.

2. University of California, Berkeley, "Securing Your Home Network," Information Security Office. The guide explains that to make a service on a home computer accessible from the internet, one must configure the router's "port forwarding" feature. The absence of this configuration keeps the service private to the local network.