Autonomous System Number (ASN)

In the routing fabric of a data centre, a MOSK cluster with Tungsten Fabric enabled can be represented either by a separate Autonomous System (AS) or as part of a bigger autonomous system. In either case, Tungsten Fabric needs to participate in the BGP peering, exchanging routes with external devices and within the cloud.

The Tungsten Fabric controller acts as an internal (iBGP) route reflector for the cloud’s AS by populating /32 routes pointing to VMs across all compute nodes as well as the cloud’s edge gateway devices in case they belong to the same AS. Apart from being an iBGP router reflector for the cloud’s AS, the Tungsten Fabric controller can act as a BGP peer for autonomous systems external to the cloud, for example, for the AS configured across the data center’s leaf-spine fabric.

The Autonomous System Number (ASN) setting contains the unique identifier of the autonomous system that the MOSK cluster with Tungsten Fabric belongs to. The ASN number does not affect the internal iBGP communication between vRouters running on the compute nodes. Such communication will work regardless of the ASN number settings. However, any network appliance that is not managed by the Tungsten Fabric control plane will have BGP configured manually. Therefore, the ASN settings should be configured accordingly on both sides. Otherwise, it would result in the inability to establish BPG sessions, regardless of whether the external device peers with Tungsten Fabric over iBGP or eBGP.

Configuring ASNs

The TFOperator custom resource enables you to define ASN settings for your Tungsten Fabric cluster.

Important

The TFOperator CR must be the only place to configure the cluster ASN. Performing these configurations through the TF web UI, CLI, or API does not provide the configuration persistency, and the settings defined this way may get reset to defaults during the cluster services restart or update.

Note

Defining the default values for ASN parameters in the TF operator CR is unnecessary.

ASN settings

Parameter

Default value

Description

BGP_ASN

64512

Defines the control node’s Autonomous System Number (ASN).

ENABLE_4BYTE_AS

FALSE

Enables the 4-byte ASN format.

Example configuration:

controllers:
  tf-config:
    provisioner:
      containers:
      - env:
        - name: BGP_ASN
          value: 64515
        - name: ENABLE_4BYTE_AS
          value: true
        name: provisioner
  tf-control:
    provisioner:
      containers:
      - env:
        - name: BGP_ASN
          value: 64515
        name: provisioner