All hosts in a physical rack are connected to both the two ToR switches with 10Gb links. On each host, NIC port 1 is connected to ToR switch 1 and NIC port 2 is connected to ToR switch 2 with Link Aggregation (LAG).
The BMC on each host is connected to the management switch over a 1G connection. This connection is used for OOB management. Both ToR switches are further connected to a pair of spine switches in a dual-LAG configuration using 40 G links. The spine switches are an aggregation layer for connecting multiple racks.
Cloud Foundation is designed to be resilient to certain network failures. The datapath between hosts and ToR switches can tolerate a failure of one link between the host and ToR switches. Between the ToR and spine switches, the system can tolerate the failure of a ToR switch and/or spine switch.