Enterprise three-tier campus network with Palo Alto Firewall securing DMZ servers (Web Server VLAN 20, DB Server VLAN 30) and core switching fabric using H3C S6520 stacked switches in HA configuration. Traffic flows from ISP through the firewall to dual 10G core switches, then via L3 aggregation switches to four L2 access switches serving PC terminals and wireless APs across VLAN 10/20/30 segments. This architecture delivers redundancy at every layer—core stack HA, dual aggregation uplinks, and multi-access switch distribution—ensuring zero single points of failure for mission-critical office and DMZ workloads. Fork this diagram on Diagrams.so to customize VLAN assignments, add additional security zones, or adapt the topology for your campus size and traffic patterns. The design follows enterprise best practices for defense-in-depth, with perimeter security, network segmentation, and resilient switching fabric.