https://docs.openshift.com/rosa/rosa_hcp/rosa-hcp-sts-creating-a-cluster-quickly.html#rosa-hcp-sts-creating-a-cluster-cli_rosa-hcp-sts-creating-a-cluster-quickly


$ rosa create cluster --cluster-name=<cluster_name> \
    --sts --mode=auto --hosted-cp --operator-roles-prefix <operator-role-prefix> \
    --oidc-config-id <ID-of-OIDC-configuration> --subnet-ids=<public-subnet-id>,<private-subnet-id>


When I ran above command I got the following Error:

W: Some subnets have been excluded because they do not fit into the Machine CIDR range
E: The number of subnets for a public hosted cluster should be at least two

Here is the config of AWS VPC:
region               = "us-east-1"
subnet_azs           = ["use1-az2"]
cluster_name         = "rosa-hcp"
vpc_cidr             = "10.0.0.0/16"
subnet_cidr_prefix   = 24

to fix this issue: 
must include  --machine-cidr=x.x.x.x/16 (Target AWS VPC CIDR)

run this command:
rosa create cluster --cluster-name=<cluster_name> 
--sts 
--mode=auto 
--hosted-cp 
--operator-roles-prefix <operator-role-prefix> 
--oidc-config-id <ID-of-OIDC-configuration> 
--subnet-ids=<public-subnet-id>,<private-subnet-id>

1. navigate to https://docs.openshift.com/rosa/rosa_hcp/rosa-hcp-sts-creating-a-cluster-quickly.html#rosa-hcp-sts-creating-a-cluster-cli_rosa-hcp-sts-creating-a-cluster-quickly
2. Copy rosa create command
3. it will return error unless added --machine-cidr=x.x.x.x/16 

W: Some subnets have been excluded because they do not fit into the Machine CIDR range
E: Could not find the following subnet provided:

I: Creating cluster ...