# list all floating IPs
openstack floating ip list
openstack floating ip show 1.2.3.4
openstack floating ip list --project ${PROJECT_ID} --long

# Allocate floating IP
openstack floating ip create public 

# Allocate specific floating IP for a project (as cloud admin)
openstack floating ip create public --floating-ip-address 10.11.12.13 --project foo-project
FLOATING_IP=$(openstack floating ip create public -c floating_ip_address -f value --floating-ip-address 10.11.12.13)

# Associate floating IP to instance
openstack server add floating ip ${INSTANCE_NAME_OR_ID} ${FLOATING_IP}

# Disassociate floating IP
openstack server remove floating ip ${INSTANCE_NAME_OR_ID} ${FLOATING_IP}

# Release floating IP
openstack floating ip delete ${FLOATING_IP}

# show used floating IPs
NETWORK_ID=$(openstack subnet list --network public -c Network -f value)
openstack ip availability show -c total_ips -c used_ips ${NETWORK_ID}

# Add floating IP to port
openstack floating ip set --port ${PORT_ID} ${FLOATING_IP}

List reserved floating IPs per project

PROJECT_IDS=$(openstack floating ip list --status DOWN  -f value -c Project | sort -u)
for PROJECT_ID in ${PROJECT_IDS}; do
    PROJECT_NAME="$(openstack project show ${PROJECT_ID} -c name -f value)"
    DOMAIN_ID="$(openstack project show ${PROJECT_ID} -c domain_id -f value)"
    DOMAIN_NAME="$(openstack domain show ${DOMAIN_ID} -c name -f value)"

    echo "# ${DOMAIN_NAME} > ${PROJECT_NAME} (${PROJECT_ID})"

    openstack floating ip list --status DOWN  --project ${PROJECT_ID} -c "Floating IP Address" -f value
    echo
done

List available / used floating IP

openstack ip availability show public

Links
https://docs.openstack.org/ocata/user-guide/cli-manage-ip-addresses.html
https://help.dreamhost.com/hc/en-us/articles/215912768-Managing-floating-IP-addresses-using-the-OpenStack-CLI