Which device is primarily responsible for managing outbound and inbound traffic based on defined rules in a network?

The device that is primarily responsible for managing outbound and inbound traffic based on defined rules in a network is a firewall. Firewalls act as a barrier between a trusted internal network and untrusted external networks, such as the internet. They monitor and control incoming and outgoing traffic based on predetermined security rules.

Firewalls can be hardware-based, software-based, or both, and their primary function is to block or allow traffic based on the organization's security policies. This is crucial for protecting sensitive data from unauthorized access and preventing various cyber threats. The rules defined in a firewall can specify which types of traffic are allowable, how they should be treated, and what actions should be taken when traffic does not conform to these rules.

In contrast, while routers direct traffic within or between networks, they do not typically make security decisions based on content. Load balancers distribute incoming traffic across multiple servers to ensure availability and reliability, but they do not inherently manage traffic based on security rules. NAT gateways, or Network Address Translation gateways, allow for the mapping of public IP addresses to private IP addresses, primarily enabling multiple devices on a local network to share a single public IP address, but they also do not handle traffic based on security policies like a firewall does.