Exploring how instances retrieve their metadata

In Chapter 3, Installing Neutron, we briefly covered the process of instances accessing metadata over the network: either through a proxy in the router namespace or the DHCP namespace. The latter is described in the following section.

The DHCP namespace

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...