In NSX 4.2.1, VPC subnets configured with external DHCP relay incorrectly provision an NSX DHCP server, causing VMs to receive IP addresses from the wrong DHCP source.

Products

• VMware NSX

Issue/Introduction

• NSX Project VPC configured for external DHCP IP allocation is assigning IP addresses from the NSX DHCP server, instead of using the DHCP relay profile to relay these requests to the external DHCP server.
• VPC subnets are configured with external DHCP relay at the VPC level, and created with "Public" access mode.
• VM's connected to the VPC segment are incorrectly receiving IP addresses from the NSX DHCP server.
  
  

Environment

VMware NSX 4.2.x prior to 4.2.3.3

Cause

During the VPC subnet creation, the relay profile path fails to get correctly copied to the VPC subnet due to a known issue with version 4.2.x

Resolution

• This is a known issue affecting VMware NSX. There is currently no resolution, but one will be included in an NSX release in the near future.
• The workaround to unblock the user is to provide a DHCP relay path under the VPC subnet payload during creation, using the below API call:
  • Patch: https://10.###.###.80/policy/api/v1/orgs/default/projects/<project_name>/vpcs/<vpc_name>/subnets/<subnet_id>

    {

      "ipv4_subnet_size": 64,
  "access_mode": "Public",
  "dhcp_config": {
    "enable_dhcp": true,
    "dhcp_relay_config_path": "/orgs/default/projects/<project_name>/infra/dhcp-relay-configs/<name_of_dhcp_relay_config>"
  }
}