Install 4.20 azure stack via UPI method, the installation got failed. Because master nodes were not added into infra_id api lb, also infra_id-internal lb was not created. Interestingly there was not any error when deploy upi/azurestack/03_infra.json

    4.20.0-0.nightly-2025-08-12-153542

    Always

    1. Run Azure stack UPI install with 4.20 nightly build
    2.
    3.
    

    Installation failed.

    Installation passed.

    1. Refer to the example job - https://prow.ci.openshift.org/view/gs/test-platform-results/logs/periodic-ci-openshift-release-master-nightly-4.20-e2e-azurestack-ovn-upi/1953143097449779200 to get details and gather log.

    2. When the issue is reproduced, master nodes were not added into infra_id api lb, also infra_id-internal lb was not created, but there was not any error when deploy upi/azurestack/03_infra.json.

Running Command: az network lb list --resource-group ci-op-8ls3p80j-ead14 -o table
Location    Name                        ProvisioningState    ResourceGroup         ResourceGuid
----------  --------------------------  -------------------  --------------------  ------------------------------------
mtcazs      ci-op-8ls3p80j-ead14-n8j7l  Succeeded            ci-op-8ls3p80j-ead14  5973e13b-aba1-46f4-be07-c1761e091851

----> Another lb named "ci-op-8ls3p80j-ead14-n8j7l-internal" is supposed to be listed, but there is not.

=> loadbalance: ci-op-8ls3p80j-ead14-n8j7l
Running Command: az network lb frontend-ip list --lb-name ci-op-8ls3p80j-ead14-n8j7l -g ci-op-8ls3p80j-ead14 > /frontend-ips.json
Name                              Provisioning State  Public IP Name                                               Public IP Address  Private IP Address
----                              ------------------  --------------                                               ----------------   -----------------
a5e4d18cb46aa46f0b072313ff88502f  Succeeded           ci-op-8ls3p80j-ead14-n8j7l-a5e4d18cb46aa46f0b072313ff88502f  10.255.96.98       N/A

======> address-pool: ci-op-8ls3p80j-ead14-n8j7l
No backend found

$ az deployment operation group list -g ci-op-8ls3p80j-ead14  -n 03_infra
[
  {
    "id": "/subscriptions/d751283a-64fa-401b-92a1-58f1750ac0a7/resourceGroups/ci-op-8ls3p80j-ead14/providers/Microsoft.Resources/deployments/03_infra/operations/D089BA597B1AE239",
    "operationId": "D089BA597B1AE239",
    "properties": {
      "duration": "PT0.3512414S",
      "provisioningOperation": "Create",
      "provisioningState": "Succeeded",
      "request": null,
      "response": null,
      "serviceRequestId": "66e800c9-055f-4499-af84-0fb64cd9470e",
      "statusCode": "Created",
      "statusMessage": null,
      "targetResource": {
        "id": "/subscriptions/d751283a-64fa-401b-92a1-58f1750ac0a7/resourceGroups/ci-op-8ls3p80j-ead14/providers/Microsoft.Network/loadBalancers/ci-op-8ls3p80j-ead14-n8j7l",
        "resourceGroup": "ci-op-8ls3p80j-ead14",
        "resourceName": "ci-op-8ls3p80j-ead14-n8j7l",
        "resourceType": "Microsoft.Network/loadBalancers"
      },
      "timestamp": "2025-08-15T06:59:00.922003+00:00",
      "trackingId": "608e3c22-3c4f-42a7-b206-fdf464e49a21"
    },
    "resourceGroup": "ci-op-8ls3p80j-ead14"
  },
  {
    "id": "/subscriptions/d751283a-64fa-401b-92a1-58f1750ac0a7/resourceGroups/ci-op-8ls3p80j-ead14/providers/Microsoft.Resources/deployments/03_infra/operations/7CCA9D236320B725",
    "operationId": "7CCA9D236320B725",
    "properties": {
      "duration": "PT9.0726543S",
      "provisioningOperation": "Create",
      "provisioningState": "Succeeded",
      "request": null,
      "response": null,
      "serviceRequestId": "e28435ba-51b8-4471-ad83-4424112b8979",
      "statusCode": "OK",
      "statusMessage": null,
      "targetResource": {
        "id": "/subscriptions/d751283a-64fa-401b-92a1-58f1750ac0a7/resourceGroups/ci-op-8ls3p80j-ead14/providers/Microsoft.Network/publicIPAddresses/ci-op-8ls3p80j-ead14-n8j7l-master-pip",
        "resourceGroup": "ci-op-8ls3p80j-ead14",
        "resourceName": "ci-op-8ls3p80j-ead14-n8j7l-master-pip",
        "resourceType": "Microsoft.Network/publicIPAddresses"
      },
      "timestamp": "2025-08-15T06:59:00.547849+00:00",
      "trackingId": "b09fe7ca-d3c4-4ceb-ad76-4810c6983b42"
    },
    "resourceGroup": "ci-op-8ls3p80j-ead14"
  },
  {
    "id": "/subscriptions/d751283a-64fa-401b-92a1-58f1750ac0a7/resourceGroups/ci-op-8ls3p80j-ead14/providers/Microsoft.Resources/deployments/03_infra/operations/6735DCCA653E4D6D",
    "operationId": "6735DCCA653E4D6D",
    "properties": {
      "duration": "PT0.4780985S",
      "provisioningOperation": "Create",
      "provisioningState": "Succeeded",
      "request": null,
      "response": null,
      "serviceRequestId": "1cc6cbbf-4587-48fa-bcf6-18725658033b",
      "statusCode": "Created",
      "statusMessage": null,
      "targetResource": {
        "id": "/subscriptions/d751283a-64fa-401b-92a1-58f1750ac0a7/resourceGroups/ci-op-8ls3p80j-ead14/providers/Microsoft.Network/loadBalancers/ci-op-8ls3p80j-ead14-n8j7l-internal",
        "resourceGroup": "ci-op-8ls3p80j-ead14",
        "resourceName": "ci-op-8ls3p80j-ead14-n8j7l-internal",
        "resourceType": "Microsoft.Network/loadBalancers"
      },
      "timestamp": "2025-08-15T06:58:51.953293+00:00",
      "trackingId": "a9b6e60e-582f-4d22-92a2-f8b7c4fa6f9d"
    },
    "resourceGroup": "ci-op-8ls3p80j-ead14"
  },
  {
    "id": "/subscriptions/d751283a-64fa-401b-92a1-58f1750ac0a7/resourceGroups/ci-op-8ls3p80j-ead14/providers/Microsoft.Resources/deployments/03_infra/operations/64E08B7CF8970DDB",
    "operationId": "64E08B7CF8970DDB",
    "properties": {
      "duration": "PT0.4616028S",
      "provisioningOperation": "Create",
      "provisioningState": "Succeeded",
      "request": null,
      "response": null,
      "serviceRequestId": "ea85c2d4-c4c2-48d3-bafa-2e686a47e8e0",
      "statusCode": "OK",
      "statusMessage": null,
      "targetResource": {
        "id": "/subscriptions/d751283a-64fa-401b-92a1-58f1750ac0a7/resourceGroups/ci-op-8ls3p80j-ead14/providers/Microsoft.Compute/availabilitySets/ci-op-8ls3p80j-ead14-n8j7l-cluster",
        "resourceGroup": "ci-op-8ls3p80j-ead14",
        "resourceName": "ci-op-8ls3p80j-ead14-n8j7l-cluster",
        "resourceType": "Microsoft.Compute/availabilitySets"
      },
      "timestamp": "2025-08-15T06:58:51.931208+00:00",
      "trackingId": "26985e89-b120-47e9-8916-dadf63fcb20b"
    },
    "resourceGroup": "ci-op-8ls3p80j-ead14"
  },
  {
    "id": "/subscriptions/d751283a-64fa-401b-92a1-58f1750ac0a7/resourceGroups/ci-op-8ls3p80j-ead14/providers/Microsoft.Resources/deployments/03_infra/operations/08584463657578600840",
    "operationId": "08584463657578600840",
    "properties": {
      "duration": "PT0.1155582S",
      "provisioningOperation": "EvaluateDeploymentOutput",
      "provisioningState": "Succeeded",
      "request": null,
      "response": null,
      "serviceRequestId": null,
      "statusCode": "OK",
      "statusMessage": null,
      "targetResource": null,
      "timestamp": "2025-08-15T06:59:01.050998+00:00",
      "trackingId": "456cab82-1385-4fbe-8f17-b7b17f202b17"
    },
    "resourceGroup": "ci-op-8ls3p80j-ead14"
  }
]

$ az network lb show \
>   --ids "/subscriptions/d751283a-64fa-401b-92a1-58f1750ac0a7/resourceGroups/ci-op-8ls3p80j-ead14/providers/Microsoft.Network/loadBalancers/ci-op-8ls3p80j-ead14-n8j7l-internal"
(ResourceNotFound) The Resource 'Microsoft.Network/loadBalancers/ci-op-8ls3p80j-ead14-n8j7l-internal' under resource group 'ci-op-8ls3p80j-ead14' was not found. For more details please go to https://aka.ms/ARMResourceNotFoundFix
Code: ResourceNotFound
Message: The Resource 'Microsoft.Network/loadBalancers/ci-op-8ls3p80j-ead14-n8j7l-internal' under resource group 'ci-op-8ls3p80j-ead14' was not found. For more details please go to https://aka.ms/ARMResourceNotFoundFix

3. 4.20 IPI on Azure stack works well; 4.19 UPI on Azure stack works well.