Which device is used to prevent traffic from one network to another network segment and is commonly used at the network perimeter?

A firewall is specifically designed to monitor and control the incoming and outgoing network traffic based on predetermined security rules. It acts as a barrier between a trusted internal network and untrusted external networks, such as the internet. This device prevents unauthorized access and can also allow or block specific types of traffic based on defined policies, which makes it essential for protecting a network segment at the perimeter.

In contrast, a switch primarily operates within the same network segment to connect devices and facilitate communication between them, without necessarily providing security features for traffic between different network segments. A router, while it can manage traffic between different networks and segments, does not inherently provide the level of security, monitoring, and control that a firewall does. A hub is an older networking device that simply relays traffic between devices on the same network without any filtering or security capabilities. Therefore, the characteristics and purpose of a firewall make it the most suitable choice for preventing traffic from one network to another at the network perimeter.