Which term describes a firewall inside a network that filters traffic between segments?

• A. Border
• B. Internal
• C. Perimeter
• D. Edge

Answer: (B)

Inside a network, you want to control traffic moving between different internal segments, such as between subnets or VLANs. A firewall placed within the network to filter this east-west traffic is called an internal firewall. It enforces policies between segments, helping prevent threats from crossing from one internal zone to another. Terms like border, perimeter, or edge describe boundaries at the outer edge of the network—between the internal network and the Internet or external networks—rather than between internal segments. So the term describing a firewall that sits inside the network and filters traffic between segments is internal firewall. This distinction matters for segmentation and defense in depth, because it addresses lateral movement and internal trust boundaries.