kubernetes/kops · error

error calculating CIDR subnet: %v

Error message

error calculating CIDR subnet: %v

What it means

utils.CalculateSubnetCIDR failed combining the parsed '/size,netnum' hint with the VPC CIDR — typically the netnum is outside the range addressable at the requested prefix size (e.g. netnum 300 for a /24 carve of the block).

Source

Thrown at upup/pkg/fi/cloudup/awstasks/subnet.go:570

func calculateSubnetCIDR(vpcCIDR, subnetCIDR *string) (*string, error) {
	if vpcCIDR == nil {
		return nil, fmt.Errorf("expecting VPC CIDR to not be <nil>")
	}
	if subnetCIDR == nil {
		return nil, fmt.Errorf("expecting subnet CIDR to not be <nil>")
	}
	if !strings.HasPrefix(aws.ToString(subnetCIDR), "/") {
		return nil, fmt.Errorf("expecting subnet cidr to start with %q: %q", "/", aws.ToString(subnetCIDR))
	}

	newSize, netNum, err := utils.ParseCIDRNotation(aws.ToString(subnetCIDR))
	if err != nil {
		return nil, fmt.Errorf("error parsing CIDR subnet: %v", err)
	}

	newCIDR, err := utils.CIDRSubnet(aws.ToString(vpcCIDR), newSize, netNum)
	if err != nil {
		return nil, fmt.Errorf("error calculating CIDR subnet: %v", err)
	}

	return aws.String(newCIDR), nil
}

View on GitHub (pinned to 4c8573c808)

Solutions

1. Pick a smaller netnum consistent with the prefix size
2. Or increase the prefix size so the netnum fits within the VPC block

When it happens

Trigger: Thrown at upup/pkg/fi/cloudup/awstasks/subnet.go:570 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of kubernetes/kops@4c8573c808 (2026-09-05). Data as JSON: /api/errors/c07fbb6834a00710. Report an issue: GitHub.