Shared and Dedicated Tier-1 Router Topologies

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This topic describes shared and dedicated Tier-1 router topologies for Enterprise PKS Kubernetes clusters on vSphere with NSX-T.

Shared Tier-1 topology is the default. This topic also explains how to define a network profile that overrides this default, to specify Dedicated Tier-1 topology for Enterprise PKS clusters.

Shared Tier-1 Topology

By default, Kubernetes clusters in Enterprise PKS with NSX-T have the Shared Tier-1 network topology, in which each cluster shares a single Tier-1 router for its external-facing components: the Kubernetes node, namespace, and NSX-T load balancer.

Note: The Shared Tier-1 topology requires NSX-T Data Center v2.5.

This topology uses a single, shared Tier-1 switch and router for each Kubernetes cluster. The shared Tier-1 model only uses one Tier-1 router and multiple logical switches connected to the shared Tier-1 to connect all Kubernetes cluster components, including:

  • Kubernetes Nodes Networks
  • Kubernetes Namespaces
  • NSX-T load balancer instances allocated for the Kubernetes cluster

Comparison to Dedicated Tier-1

Unlike the Dedicated Tier-1 Topology, the shared Tier-1 model configures any necessary NAT rules (if using NAT mode) on the single Tier-1 router directly. The Tier-0 router is not used for any NAT configuration. As a result, the Tier-0 router can operate in Active/Active mode if all Kubernetes clusters are deployed using the Shared Tier-1 model.

The Shared Tier-1 model enables higher scale numbers for PKS as the number of NSX-T objects allocated per Kubernetes cluster is drastically reduced, in comparison to dedicated Tier-1. The advantage of the shared Tier-1 topology is that you can increase the number of NSX-T objects that can be supported in a given cluster.

Dedicated Tier-1 Topology

When you provision a Kubernetes cluster with a network profile that overrides the Shared Tier-1 topology, Enterprise PKS creates following NSX-T objects:

  • 1 Logical Switch and Tier-1 Router for each Kubernetes Nodes subnet
  • 1 Logical Switch and Tier-1 Router for each Kubernetes namespace
  • 1 Logical Switch and Tier-1 Router each NSX-T Load Balancer that is allocated for the Kubernetes cluster

As depicted above, the result is that a given Kubernetes cluster will run several Tier-1 switches and routers in its topology.

Network Profile for Dedicated Tier-1 Topology

To create clusters with Dedicated Tier-1 topology, you define and use a network profile that overrides the default Shared Tier-1 topology by setting the single_tier_topology key to false.

Shown below is an example network profile that disables the Shared Tier-1 Router for Kubernetes clusters:

{
  "name": "example-network-profile-shared-t1",
  "description": "Shared-Tier-1 topology network profile",
  "parameters": {
    "single_tier_topology": false
  }
}

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