By default, ACI-wide flooding is disabled. Because flooding is disabled, connecting to a DHCP server is only possible if it is in the same EPG as the client (as flooding within a bridge domain is enabled).
The options, therefore, are to have one DHCP server per-EPG, which would be wasteful on "compute" resources and on administrative time, or to use a DHCP relay and have one, central, server.
In this recipe, we will be setting up a DHCP relay.
We will be using the Common tenant for this (first), as it is best practice to place resources within this tenant if they are to be shared across multiple tenants. Using the Common tenant is not the only way, though; we can also use the Fabric Access policies to achieve the same goal for the Infrastructure tenant.