Redundancy and high availability in networks come from having multiple paths and the ability to share load across links. Spanning Tree Protocol prevents switching loops by electing a root and blocking some redundant links, then re-enabling them if an active path fails. This creates an alternate path so connectivity isn’t lost. Link Aggregation Control Protocol groups several physical links into one logical path, which increases total bandwidth and lets traffic continue on the remaining links if one member fails. In short, STP provides safe, alternate routing to stay connected, while LACP enables bandwidth sharing and resilience across multiple links. The other options involve services and application protocols rather than the mechanisms that ensure network path redundancy and link-level load balancing.

Layer 2 forwarding uses MAC addresses to move frames within a local network. A switch is designed for this role: it builds a MAC address table by listening to each frame’s source address and the port it arrives on. With that knowledge, it forwards a frame destined for a known MAC only to the specific port where that device can be reached. If the destination MAC isn’t yet in the table, the switch sends the frame to all ports (except the source) so the destination can respond and the address can be learned. This targeted forwarding reduces unnecessary traffic and creates separate collision domains per port, improving efficiency compared to devices that don’t inspect MAC addresses. In contrast, a hub or a repeater operates at Layer 1 and simply repeats signals to all ports, keeping a single shared collision domain. A router works at Layer 3 and routes traffic between different networks using IP addresses, not for forwarding within a single LAN.

Spoofing is the technique where an attacker pretends to be a trusted source, crafting transmissions that look legitimate to the victim’s device or network. By forging identifiers such as the source IP address, MAC address, or email header, the attacker aims to bypass trust checks and get the victim to accept or act on the communication. This can enable things like intercepting traffic (man-in-the-middle), phishing, or data exfiltration because the system believes the data is coming from a legitimate, trustworthy source. Flooding would overwhelm a network with traffic and doesn’t involve making transmissions appear legitimate. CAM (Content-Addressable Memory) relates to fast lookups in networking hardware rather than deception. DRM (Digital Rights Management) governs how content is used and isn’t about impersonating sources.

Inter-VLAN routing is needed because VLANs create separate broadcast domains, so devices in different VLANs can’t communicate just by switching frames. To move traffic between these networks, a device that can perform IP routing is required. A router handles this by connecting to each VLAN (often via subinterfaces on a trunk with 802.1Q tagging) and giving each VLAN its own subnet and gateway IP. In many modern networks, a Layer 3 switch provides the same capability directly on the switch, using SVIs or routed ports for each VLAN so traffic between VLANs is routed in hardware. End-user devices don’t perform inter-VLAN routing; they rely on a gateway. A firewall can route, but the standard, widely applicable device for this function is a router or a Layer 3 switch.