1 Network Topology
1.1 Access-Aggregation-Core
Firewalls, load balancers, and core switches should all have redundancy; at least two units are required. Access-Aggr-Core design prioritizes north-sourth traffic (client-to-server flows).
Internet <---> FW <---> DMZ <---> FW <---> Intranet
1.2 Leaf-Spine
Leaf-spine architecture is primarily designed to optimize east–west traffic within data center environments. leaf-spine assumes most communication occurs between servers. Every leaf switch connects to all spine switches, creating multiple equal-cost paths between any two endpoints.
For more details, see til/net/data-center