Managed cluster networking

A Kubernetes cluster networking is typically focused on connecting pods on different nodes. On bare metal, however, the cluster networking is more complex as it needs to facilitate many different types of traffic.

Kubernetes clusters managed by Mirantis Container Cloud have the following types of traffic:

  • PXE network

    Enables the PXE boot of all bare metal machines in Container Cloud. This network is not configured on the hosts in a managed cluster. It is used by the bare metal provider to provision additional hosts in managed clusters and is disabled on the hosts after provisioning is done.

  • Life-cycle management (LCM) network

    Connects LCM Agents running on the hosts to the Container Cloud LCM API. The LCM API is provided by the regional or management cluster. The LCM network is also used for communication between kubelet and the Kubernetes API server inside a Kubernetes cluster. The MKE components use this network for communication inside a swarm cluster.

    When using the BGP announcement of the IP address for the cluster API load balancer, which is available as Technology Preview since Container Cloud 2.24.4, no segment stretching is required between Kubernetes master nodes. Also, in this scenario, the load balancer IP address is not required to match the LCM subnet CIDR address.

    • LCM subnet(s)

      Provides IP addresses that are statically allocated by the IPAM service to bare metal hosts. This network must be connected to the Kubernetes API endpoint of the regional cluster through an IP router. LCM Agents running on managed clusters will connect to the regional cluster API through this router. LCM subnets may be different per managed cluster as long as this connection requirement is satisfied. The Virtual IP (VIP) address for load balancer that enables access to the Kubernetes API of the managed cluster must be allocated from the LCM subnet.

    • Cluster API subnet

      Technology Preview

      Provides a load balancer IP address for external access to the cluster API. Mirantis recommends that this subnet stays unique per managed cluster.

  • Kubernetes workloads network

    Serves as an underlay network for traffic between pods in the managed cluster. Do not share this network between clusters.

    • Kubernetes workloads subnet(s)

      Provides IP addresses that are statically allocated by the IPAM service to all nodes and that are used by Calico for cross-node communication inside a cluster. By default, VXLAN overlay is used for Calico cross-node communication.

  • Kubernetes external network

    Serves ingress traffic to the managed cluster from the outside world. You can share this network between clusters, but with dedicated subnets per cluster. Several or all cluster nodes must be connected to this network. Traffic from external users to the externally available Kubernetes load-balanced services comes through the nodes that are connected to this network.

    • Services subnet(s)

      Provides IP addresses for externally available Kubernetes load-balanced services. The address ranges for MetalLB are assigned from this subnet. There can be several subnets per managed cluster that define the address ranges or address pools for MetalLB.

    • External subnet(s)

      Provides IP addresses that are statically allocated by the IPAM service to nodes. The IP gateway in this network is used as the default route on all nodes that are connected to this network. This network allows external users to connect to the cluster services exposed as Kubernetes load-balanced services. MetalLB speakers must run on the same nodes. For details, see Configure node selector for MetalLB speaker.

  • Storage network

    Serves storage access and replication traffic from and to Ceph OSD services. The storage network does not need to be connected to any IP routers and does not require external access, unless you want to use Ceph from outside of a Kubernetes cluster. To use a dedicated storage network, define and configure both subnets listed below.

    • Storage access subnet(s)

      Provides IP addresses that are statically allocated by the IPAM service to Ceph nodes. The Ceph OSD services bind to these addresses on their respective nodes. Serves Ceph access traffic from and to storage clients. This is a public network in Ceph terms. 1

    • Storage replication subnet(s)

      Provides IP addresses that are statically allocated by the IPAM service to Ceph nodes. The Ceph OSD services bind to these addresses on their respective nodes. Serves Ceph internal replication traffic. This is a cluster network in Ceph terms. 1

  • Out-of-Band (OOB) network

    Connects baseboard management controllers (BMCs) of the bare metal hosts. This network must not be accessible from the managed clusters.

The following diagram illustrates the networking schema of the Container Cloud deployment on bare metal with a managed cluster:

../../../_images/bm-cluster-l3-networking-multihomed.png
1(1,2)

For more details about Ceph networks, see Ceph Network Configuration Reference.