The DHCP service for a given network is something often taken for granted and is not directly seen, let alone configurable, by users or operators via the API. Neutron has scheduled DHCP services across multiple DHCP agents for some time using the following configuration option in the Neutron configuration file at /etc/neutron/neutron.conf:

# Number of DHCP agents scheduled to host a tenant network.
# If this number isgreaterthan 1, the scheduler automatically
# assigns multiple DHCP agents for a given tenant network,
# providing high availability for DHCP service.
# (integer value)
# dhcp_agents_per_network = 1 

When dhcp_agents_per_network is greater than 1, and more than one DHCP agent exists in the environment, Neutron will automatically schedule a network to multiple DHCP agents up to the specified value. Using the openstack network create command with the --availability-zone-hint argument, we can suggest to the scheduler that DHCP services be split amongst multiple availability zones as shown here:

openstack network create network01
--availability-zone-hint AZ1
--availability-zone-hint AZ2 

Directing a network's DHCP services to a particular availability zone does not ensure it will be scheduled to a DHCP agent in that zone, however, as the directive is more of a scheduler hint than an outright requirement. Neutron performs best effort scheduling using availability zone hints. Multiple availability zones can be specified, if desired, by repeating the --availability-zone-hint argument as necessary.

More information on the use of network availability zones can be found in upstream documentation available at the following URL: https://docs.openstack.org/neutron/pike/admin/config-az.html.