VMware NSX Alams UI displays "IP block usage very high"
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VMware NSX Alams UI displays "IP block usage very high"


Article ID: 367162


Updated On:


VMware NSX Networking


This article provides resolution to resolve issue, when the VMware NSX Home > Alarms UI displays the following event:

Event ID: IP Block Usage Very High


VMware NSX 3.1.2


While creating the subnet from the IPBlock, VMware NSX checks that the total remaining available range for allocation should not be less than 10%. If the remaining available range for further subnet creation is less than 10%, VMware NSX raises an alarm.


Note: A maintenance window is not required for remediation.


Review the IP block usage. Use a new IP block for resource creation or delete unused IP subnet from the IP block. To check subnet being used for IP Block:

  1. From the NSX UI, navigate to Networking | IP Address pools | IP Address Blocks tab.
  2. Click View Statistics beside the IP Block and check the used and available IP ranges
  3. Select IP pools where IP block being used, check the Subnets and Allocated IPs column on the UI. If no allocation has been used for the IP pool and it is not going to be used in the future, then delete subnet or IP pool.
  4. Use following API to check if IP block being used by IP pool and also check if any IP allocation has been done.
    • To check the usage of an IP Block:
      invoke NSX API: GET /policy/api/v1/infra/ip-blocks/<ip-block-id>/usage
    • To get configured subnets of an IP pool:
      invoke the NSX API:  GET /policy/api/v1/infra/ip-pools/<ip-pool>/ip-subnets
    • To get IP allocations:
      invoke the NSX API: GET /policy/api/v1/infra/ip-pools/<ip-pool>/ip-allocations

Note: Deletion of IP pool/subnet should only be done if it does not have any allocated IPs and it is not going to be used in future. Contact VMware support if you require any assistance.


You may not be able to create a subnet in future, due to limited IPs available in block for allocation.


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