NSX Gateway DHCP is configured but VMs do not get an IP address

Products

• VMware NSX

Issue/Introduction

• VMware NSX
• Under Networking -> Segments, DHCP Type drop-down menu, observe that Gateway DHCP Server has been configured
• Virtual Machines on the segment do not get a DHCP address
• Under Networking  -> Tier-1 Gateways -> T1 Gateway ->  DHCP Config -> View Statistics, no DHCP Discovers have been received by the Gateway
  
  

Environment

VMware NSX

Cause

By default DFW rules are applied to VMs connected to a NSX managed networks. When Reject/Block rules exist then an explicit allow rule for DHCP traffic must be configured.

Resolution

Under Security -> Distributed firewall, configure an Allow rule for source any, destination any and service type DHCP-client, DHCP-server.

As DFW rules are evaluated top down within a section, e.g. Application, and sections are evaluated from left to right, ensure a deny rule does not exist higher up or in previous section.