Final answer:
A firewall is the device that filters packets to isolate a network, acting as a barrier and protecting the network from external threats.
Step-by-step explanation:
The type of device that isolates a network by filtering the packets that can enter it is known as a firewall. A firewall acts as a barrier between a trusted internal network and untrusted external networks such as the internet. It examines incoming and outgoing network traffic based on predetermined security rules and filters traffic to protect the network from unauthorized access, cyber threats, and malicious activities.
A bridge is used to connect multiple network segments at the data link layer. A gateway is a network point that acts as an entrance to another network, often involving different protocols. A switch is used to connect devices within a network by using packet switching to receive, process, and forward data to the destination device.