IP Pool Usage Very High Alarm is not triggered in NSX manager mode

Products

• VMware NSX

Issue/Introduction

When monitoring IP Pools under Networking → IP Address Management → IP Pools in NSX Manager, you may observe that the IP Pool usage is very high under Allocations.

However, even if the thresholds for the “IP Pool Usage Very High” alarm are set (for example, 20% or 90%), no alarm is triggered.

This behavior can occur when IP Pools are created and used in Manager mode, such as with TKGI clusters, where IP allocations are made from a Manager-level IP Pool. In such cases, even if utilization exceeds 90% (for example, 272 out of 313 IPs used), NSX will not raise an alarm

Environment

VMware NSX

VMware NSX-T Datacenter 

Cause

The “IPAM IP Pool Usage Very High” alarm is triggered by the IpAllocation intent creation event. If the system allocates IP's using Management Plane (MP) APIs instead of creating a Policy IpAllocation intent, the trigger for alarm creation does not occur, even if the IP usage is high. This behavior is by design.

IPAM alarms (such as “IP Pool Usage Very High”) are generated only for Policy mode objects (create/update/delete actions).

When IP allocations are made in Manager mode, the Policy event required for alarm generation is never invoked, therefore, no alarm is raised.

Resolution

• To monitor IP usage for Manager mode pools, use the NSX API to check utilization manually:

API Request:

GET https://<nsx-manager-IP>/api/v1/pools/ip-pools/<pool-id>

This API provides details of IP allocation and usage for the specified pool.

example response -
{      
        "_create_time": 1567433347564,
        "_create_user": "admin",
        "_last_modified_time": 1745853969160,
        "_last_modified_user": "admin",
        "_protection": "NOT_PROTECTED",
        "_revision": 14,
        "_system_owned": false,
        "check_overlap_with_existing_pools": false,
        "description": "provisioned by Terraform, used in TKGI network profile",
        "display_name": "pks-vip-pool",
        "id": "##########",
        "ip_address_type": "IPV4",
        "pool_usage": {                                           <<<<<<<
          "allocated_ids": 277,
          "free_ids": 36,
          "total_ids": 313
        },  
        "resource_type": "IpPool",
        "subnets": [

• The same can be seen in Manager UI -

Navigate to NSX UI Networking → IP Address Management → IP Pools tab , you can see the number of allocations made from a pool in the last column 

• Follow technical document to promote manager object to policy objects