Anthos on bare metal requires only L3 connectivity for worker nodes but requires L2 connectivity among control plane nodes to announce virtual IP addresses (VIP)s. The load balancer can be run on a separate node pool or on the control plane node pool. The same L2 network requirements apply if the load balancer is run on the control plane node pool.
Control-plane traffic goes through the control plane VIP, so load balancer setup is required during cluster startup.
The requirements for load balancer machines are:
The following figure shows the logical configuration of an Anthos on bare metal environment with a non-HA control plane:
The following figure shows the logical configuration of bare metal environment with a HA control plane: