Which of the following is NOT a primary function of a router?

Routers primarily function to manage traffic between networks, forward data packets to their intended IP addresses, and allow multiple devices to share the same IP address through either dynamic or static address allocation methods, such as Network Address Translation (NAT).

While routers can include some basic firewall features as part of their functionality, providing comprehensive firewall protection is not considered one of their primary functions. Routers primarily focus on directing data traffic efficiently and connecting different networks. Firewalls, on the other hand, are dedicated security devices designed specifically to filter traffic based on predetermined security rules, protecting individual devices or entire networks from unauthorized access and attacks.

Thus, while a router may have some security capabilities, it's not their main role; therefore, comprehensive firewall protection for each connected device is not a primary function of a router.