kubernetes/kops · error

expecting subnet CIDR to not be <nil>

Error message

expecting subnet CIDR to not be <nil>

What it means

calculateSubnetCIDR was asked to compute a CIDR but the subnet's CIDR hint pointer is nil — the spec is incomplete: a subnet expects a computed CIDR without providing the '/size,netnum' hint.

Source

Thrown at upup/pkg/fi/cloudup/awstasks/subnet.go:557

func (d *deleteSubnetIPv6CIDRBlock) TaskName() string {
	return "SubnetIPv6CIDRBlock"
}

func (d *deleteSubnetIPv6CIDRBlock) Item() string {
	return fmt.Sprintf("%v: ipv6cidr=%v", *d.vpcID, *d.ipv6CidrBlock)
}

func (d *deleteSubnetIPv6CIDRBlock) DeferDeletion() bool {
	return false // TODO: should we defer this?
}

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. Set the subnet's CIDR hint (e.g. '/24,3') or an explicit CIDR in the cluster spec
2. Re-run `kops update cluster` after fixing the subnet spec

When it happens

Trigger: Thrown at upup/pkg/fi/cloudup/awstasks/subnet.go:557 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/9f0e564bee10807c. Report an issue: GitHub.