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