Scalable groups provide intra-VN traffic filtering and control in Cisco SD-Access. Within a virtual network, macro segmentation separates routing tables, but endpoints inside the same VN may still need policy control based on identity, role, or security posture. Cisco SD-Access uses scalable group tags and scalable group ACLs to implement group-based policy. This allows policy to be expressed as user or device group relationships instead of only subnet-based ACL entries. The result is microsegmentation inside the virtual network, where traffic between groups can be permitted or denied consistently across the fabric. MAC ACLs are limited Layer 2 filters and do not provide the identity-based policy model required for SD-Access. Prefix lists are route-filtering tools, not intra-VN access-control mechanisms. Service policies are used for QoS or traffic treatment and do not define group-based segmentation. Scalable groups are therefore the correct policy construct for intra-VN filtering in the fabric. Reference topics: Cisco SD-Access policy, scalable groups, SGT, SGACL, microsegmentation, intra-VN control.