create a IBMCloud cluster with an existed VPC, which has 15 subnets, often failed. 

4.17, 4.18  4.16

often    

    1.create a vpc,create gateway in each zone,and total add 15 subnets.
    2.based on the vpc, preapare the install-config as the following:
platform:
  ibmcloud:
    region: jp-tok
    networkResourceGroupName: ci-op-6lygc8z1-771f9-rg
    vpcName: ci-op-6lygc8z1-771f9-vpc
    controlPlaneSubnets:
    - ci-op-6lygc8z1-771f9-control-plane-3-3
    - ci-op-6lygc8z1-771f9-control-plane-3-2
    - ci-op-6lygc8z1-771f9-control-plane-3-1
    - ci-op-6lygc8z1-771f9-control-plane-2-3
    - ci-op-6lygc8z1-771f9-control-plane-2-2
    - ci-op-6lygc8z1-771f9-control-plane-2-1
    - ci-op-6lygc8z1-771f9-control-plane-1-3
    - ci-op-6lygc8z1-771f9-control-plane-1-2
    - ci-op-6lygc8z1-771f9-control-plane-1-1
    - ci-op-6lygc8z1-771f9-control-plane-jp-tok-3
    - ci-op-6lygc8z1-771f9-control-plane-jp-tok-2
    - ci-op-6lygc8z1-771f9-control-plane-jp-tok-1
    computeSubnets:
    - ci-op-6lygc8z1-771f9-compute-jp-tok-3
    - ci-op-6lygc8z1-771f9-compute-jp-tok-2
    - ci-op-6lygc8z1-771f9-compute-jp-tok-1
    resourceGroupName: ci-op-6lygc8z1-771f9-rg     

3.create cluster    

install failed
$oc get co
ingress                                    4.17.0-0.nightly-2024-10-30-021005   True        False         True       50m     The "default" ingress controller reports Degraded=True: DegradedConditions: One or more other status conditions indicate a degraded state: CanaryChecksSucceeding=False (CanaryChecksRepetitiveFailures: Canary route checks for the default ingress controller are failing. Last 1 error messages:...

$ROUTE=$(oc get route -n openshift-ingress-canary -ojsonpath={..host})
$ for i in `oc get po -n openshift-ingress-operator | grep -v NAME| awk '{print $1}' ` ; do oc exec -n openshift-ingress-operator -c ingress-operator $i -- curl http://${ROUTE} -sS -k -D - ; done
curl: (52) Empty reply from server
command terminated with exit code 52

install the cluster succeed.    

1. https://docs.openshift.com/container-platform/4.17/installing/installing_ibm_cloud/installing-ibm-cloud-vpc.html
2.https://cloud.ibm.com/docs/vpc?topic=vpc-load-balancer-faqs#max-number-subnets-alb 
15 is the maximum number of subnets that you can define with your ALB (Application Load Balancer for VPC).