Resolving Duplicate IP Assignment Issues When adding a new Host to an NSX Prepared Cluster.
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Resolving Duplicate IP Assignment Issues When adding a new Host to an NSX Prepared Cluster.

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Article ID: 390030

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Updated On: 03-20-2025

Products

VMware NSX

Issue/Introduction

  • Adding a new host to an NSX prepared cluster leads to a duplicate IP address being assigned to it.

  • The hosts are prepared using a IP pool in NSX, there are sufficient IP's in the pool to assign to the hosts and spare unused IP addresses.

  • When checking the IP Pool , we can see the duplicate IP being assigned is not present in the list of allocated IPs, even though there is a host using this IP when viewing under System>Fabric>Hosts>Host TEP IP.

  • The number of allocated IPs in the Pool is less than TEP IPs actually in use by the hosts in the cluster. e.g, if a cluster has 5 hosts with 2 TEP IPs each (total 10 IPs) the IP Pool will have a lesser number of IPs under the allocated list.

  • Entries similar to the below are observed in ESXI logs:/var/run/log/vobd.log:

2025-01-28T15:06:47.382Z: [netCorrelator] 8492350294662us: [esx.problem.net.vmknic.ip.duplicate] Duplicate IP address detected for 172.###.###.226 on interface vmk3, current owner being 00:50:##:##:21:d2.
2025-01-28T15:06:47.675Z: [netCorrelator] 8492323880740us: [vob.net.vmknic.ip.duplicate] A duplicate IP address was detected for 172.###.###.228 on interface vmk4. The current owner is 00:50:##:##:58:bb.

2025-01-28T15:59:42.701Z: [netCorrelator] 8495366153398us: [vob.net.vmknic.ip.duplicate] A duplicate IP address was detected for 172.##.##.232 on interface vmk3. The current owner is 00:50:##:##:ce:05.

2025-01-28T15:59:42.939Z: [netCorrelator] 8495366391665us: [vob.net.vmknic.ip.duplicate] A duplicate IP address was detected for 172.##.##.235 on interface vmk4. The current owner is 00:50:##:##:3f:ea.

Environment

VMware NSX 3.2.1 and below.

Cause

When creating or updating a Transport Node (preparing NSX), if the operation fails, the Transport Node may release its TEP IP address, even though it is still in use. This IP address could then be reassigned to another Transport Node in the future, leading to potential duplicate TEP IP issues.

Resolution

This issue is resolved in NSX 3.2.2, 3.2.3 and 4.0.1 and above, available at Broadcom downloads.

If you are having difficulty finding and downloading software, please review the Download Broadcom products and software KB

Workaround:

To resolve the issue of non-allocated IPs within an IP pool, follow the steps below:

1. Identify Non-Allocated IPs

Use the following API to retrieve the IP allocations within the specified IP pool:

GET https://<nsx-mgr-ip>/policy/api/v1/pools/ip-pools/<mp-pool-id>/allocations

Sample output

{
    "results": [
        {
            "allocation_id": "192.168.141.11",
            "_protection": "NOT_PROTECTED"
        },
        {
            "allocation_id": "192.168.141.14",
            "_protection": "NOT_PROTECTED"
        },
        {
            "allocation_id": "192.168.141.12",
            "_protection": "NOT_PROTECTED"
        }
    ],
    "result_count": 3
}

Review the response to identify IP addresses that have not been allocated (non-allocated IPs)

2. Manually Allocate IPs

Once you have identified the non-allocated IP addresses, you can manually allocate them to the required IP Pool. Use the following API to allocate the IP:


https://<nsx-mgr-ip>/api/v1/pools/ip-pools/<mp-pool-id>?action=ALLOCATE

Request Body:

{
   "allocation_id": "<ip-from-step-1>"
}


3. Verify Allocation

After manually allocating the IP addresses, use the same API from Step 1 to verify that the allocation has been successfully applied. This ensures that the IP has been correctly assigned and is no longer in the non-allocated state.


By following these steps, you should be able to resolve any issues related to unassigned IP addresses in the IP pool.

Additional Information

If you are contacting Broadcom support about this issue, please provide the following:

  • NSX Manager support bundles
  • ESXi host support bundles for hosts that are failing to configure as transport nodes.
  • Text of any error messages seen in NSX GUI or command lines pertinent to the investigation.

Handling Log Bundles for offline review with Broadcom support.