Which of the following allows logical isolation of hosts on a network?

Logical isolation of hosts on a network is achieved through a VLAN (Virtual Local Area Network). VLANs allow network administrators to segment a physical network into multiple logical networks. This means that hosts can be grouped together based on organizational needs without regard to their physical location within the network. By assigning different VLANs to various groups, broadcast traffic is kept within the VLAN, reducing overall congestion and improving network efficiency.

VLANs enhance security by limiting communication to designated segments, thus providing a level of isolation between different groups of users or devices. For example, you could have one VLAN for sensitive data processing and another for general use, preventing users in the general VLAN from accessing resources in the sensitive VLAN.

In contrast, technologies like DNS (Domain Name System), TLS (Transport Layer Security), and IPSec (Internet Protocol Security) serve different purposes. DNS is primarily used for resolving domain names to IP addresses, TLS is focused on securing communications over a network, and IPSec provides encryption and integrity for IP packets but does not create logical segmentation of the network. Thus, VLANs are the key technology for achieving logical isolation of hosts on a network.