Anthos on bare metal only requires L3 connectivity for worker nodes, but requires L2 connectivity among control plane nodes to announce VIPs. 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 all 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 describes the logical configuration of an Anthos on bare metal environment with a non-HA control plane:

Figure 8.                  Bare metal environment with non-HA control plane.

• The control plane nodes run load balancers, and they are all on the same L2 network, while other connections, including worker nodes, only require 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 describes the logical configuration of bare metal environment with a HA control plane:

Figure 9.                  Bare metal environment with HA control plane