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:

• All load balancers are in the same L2 subnet.
• All VIPs must be in the load balancer machine subnet and routable to the gateway of the subnet.

The following figure shows the logical configuration of an Anthos on bare metal environment with a non-HA control plane:

Figure 12: Bare metal environment with non-HA control plane

• The control plane nodes run load balancers. The load balancers are all on the same L2 network, while other connections, including worker nodes, require only L3 connectivity.
• Configuration files define IP addresses for worker node pools, virtual IP addresses for services, ingress, and control plane (Kubernetes API) access.
• A connection to Google Cloud is also required.

The following figure shows the logical configuration of bare metal environment with a HA control plane:

Figure 13: Bare metal environment with HA control plane