Design a spine-leaf fabric for a new data hall

You are designing the network for a new data hall. At launch there are 600 servers, growing to 1,000 within three years. Each server has two 25G NICs and racks hold 40 servers. Some VM clusters need the same subnet in several racks. Two tenants, PROD and DEV, may only talk to each other through a firewall. Two WAN routers connect the site. The approved hardware is fixed-form-factor: leaves with 48 x 25G and 6 x 100G ports, spines with 64 x 100G ports. Leaf oversubscription must be 3:1 or better.