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Subnet Available

Subnet Available Collector​

To check if there is an available (IPv4) subnet on a node, you can use the subnetAvailable collector. This is useful for Pod/Service CIDR ranges.

This collector searches for overlap with the routing table of the node to help avoid conflicts.

Parameters​

In addition to the shared collector properties, the subnetAvailable collector accepts the following parameters:

CIDRRangeAlloc (Required)​

The overarching subnet range to search for available CIDR blocks to use. The format must be "x.x.x.x/y", with an IPv4 network and y being a CIDR mask between 1 and 32.

desiredCIDR (Required)​

An integer between 1 and 32.

Searches in CIDRRangeAlloc for an IP subnet of this CIDR block size.

Example Collector Definition​

apiVersion: troubleshoot.sh/v1beta2
kind: HostPreflight
metadata:
  name: subnet-available
spec:
  collectors:
    # would output yes/no depending if there is a /22 available in 10.0.0.0/8
    - subnetAvailable:
        CIDRRangeAlloc: "10.0.0.0/8"
        desiredCIDR: 22

Included Resources​

The results of the subnetAvailable collector are stored in the host-collectors/subnetAvailable directory of the support bundle.

[collector-name].json​

If the collectorName field is not set, the file is named result.json.

Example of the resulting JSON file:

{
  "CIDRRangeAlloc": "10.0.0.0/8",
  "desiredCIDR": 22,
  "status": "a-subnet-is-available"
}

Subnet Available Analyzer​

The subnetAvailable analyzer supports the following outcomes:

  • a-subnet-is-available: Indicates that a subnet of the desiredCIDR size is available within CIDRRangeAlloc.
  • no-subnet-available: Indicates that the entirety of CIDRRangeAlloc is exhausted by the node routing table, and that no subnets can be allocated of the desiredCIDR size.

Example Analyzer Definition​

apiVersion: troubleshoot.sh/v1beta2
kind: HostPreflight
metadata:
  name: subnet-available
spec:
  analyzers:
    - subnetAvailable:
        outcomes:
          - fail:
            when: "no-subnet-available"
            message: failed to find available subnet
          - pass:
            when: "a-subnet-is-available"
            message: available /22 subnet found