Instances access metadata at http://169.254.169.254, followed by a URI that corresponds to the version of metadata, which is usually /latest. When an instance is connected to a network that does not utilize a Neutron router as the gateway, the instance must learn how to reach the metadata service. This can be accomplished in a few different ways, including the following:

• Setting a route manually on the instance
• Allowing DHCP to provide a route

When enable_isolated_metadata is set to True in the DHCP configuration file at /etc/neutron/dhcp_agent.ini, each DHCP namespace provides a proxy to the metadata service running on the controller node(s). The proxy service listens directly on port 80, as shown in the following screenshot:

Using the ps command within the namespace, you can see the process associated with this listener is the Neutron metadata proxy: