With a metadata proxy server, VM instances can retrieve instance-specific metadata from an OpenStack Nova API server.

The following steps describe how a metadata proxy works:

  1. A VM sends an HTTP GET to http://169.254.169.254:80 to request some metadata.
  2. The metadata proxy server that is connected to the same logical switch as the VM reads the request, makes appropriate changes to the headers, and forwards the request to the Nova API server.
  3. The Nova API server requests and receives information about the VM from the Neutron server.
  4. The Nova API server finds the metadata and sends it to the metadata proxy server.
  5. The metadata proxy server forwards the metadata to the VM.

A metadata proxy server runs on an NSX Edge node. For high availability, you can configure metadata proxy to run on two or more NSX Edge nodes in an NSX Edge cluster.