The requirement is to prevent communication between devices within the same VLAN without using dynamic access control lists (dACLs). Cisco TrustSec is the technology designed for this purpose. It provides micro-segmentation by assigning Security Group Tags (SGTs) to endpoints based on their identity or role, as determined by Cisco ISE. Network devices, such as switches, then enforce communication policies using a Security Group ACL (SGACL) matrix. This allows for granular, identity-based policy enforcement that is independent of network topology (like VLANs or IP subnets), effectively isolating hosts even if they reside on the same logical network segment.

A. Implement device posturing: Posturing assesses an endpoint's security compliance (e.g., antivirus status) to determine its level of network access, but it does not enforce traffic policies between devices.

B. Set up endpoint profiling: Profiling identifies and classifies endpoints to inform policy decisions (like assigning a VLAN or SGT), but it is not the mechanism that enforces the communication rules.

C. Enable identity groups: Identity groups are logical containers within ISE used to group users or endpoints for easier policy management; they do not directly implement traffic segmentation on the network.

1. Cisco Identity Services Engine Administrator Guide, Release 3.1, "TrustSec" Chapter, "Cisco TrustSec Solution" section: "Cisco TrustSec technology provides network segmentation by using security groups. This segmentation simplifies network management by defining security policies that are independent of the network topology. In a Cisco TrustSec-enabled network, you can provision network access control based on the user and device identity and roles, and not IP addresses." This highlights that TrustSec operates independently of VLANs and IP-based ACLs.

2. Cisco SD-Access Solution Design Guide (CVD), Chapter 2: "Solution Components and Architecture", Section: "Group-Based Policy": "Micro-segmentation... provides for the ability to create granular policies that can limit the lateral movement of a threat... This is accomplished by using Cisco TrustSec technology with security group tags (SGTs) that represent a logical grouping of users and things. The policy between SGTs is represented in a matrix form, which is centrally managed from Cisco ISE and pushed to the network devices for enforcement." This confirms TrustSec's role in granular, intra-segment policy enforcement.

3. TrustSec Segmentation and Policy Enforcement Design Guide, "Introduction to TrustSec" section: "TrustSec provides topological-independent, role-based segmentation... This is a significant improvement over traditional segmentation methods that rely on VLANs, ACLs, and firewall rules... Policy enforcement is performed on the destination network device by comparing the SGT of the source with the DGT (Destination Group Tag) of the destination in the SGACL matrix." This explicitly contrasts TrustSec with traditional ACLs and confirms its mechanism for intra-VLAN segmentation.