I have followed the instructions from https://docs.openstack.org/install-guide/ to install openstack Ussuri where i use a controller node and a compute node (i can ping each  other and access the internet from both nodes through the mgmt iface).

I use ubuntu 18.04 for all components.

I have configured the network option 2, seems to work fine:

openstack network agent list
+--------------------------------------+--------------------+------------+-------------------+-------+-------+---------------------------+
| ID                                   | Agent Type         | Host       | Availability Zone | Alive | State | Binary                    |
+--------------------------------------+--------------------+------------+-------------------+-------+-------+---------------------------+
| 2d8c3a89-32c4-4b97-aa4f-ca19db53b24f | L3 agent           | controller | nova              | :-)   | UP    | neutron-l3-agent          |
| 413cd13d-88d7-45ce-8b2e-26fdb265740f | Metadata agent     | controller | None              | :-)   | UP    | neutron-metadata-agent    |
| 42f57bee-63b3-44e6-9392-939ece98719d | Linux bridge agent | compute    | None              | :-)   | UP    | neutron-linuxbridge-agent |
| 4a787a09-04aa-4350-bd32-0c0177ed06a1 | DHCP agent         | controller | nova              | :-)   | UP    | neutron-dhcp-agent        |
| fdafc337-7581-4ecd-b175-810713a25e1f | Linux bridge agent | controller | None              | :-)   | UP    | neutron-linuxbridge-agent |
+--------------------------------------+--------------------+------------+-------------------+-------+-------+---------------------------+

If i try to bring up instances connected by an internal network, they are successfully deployed.

When i use the provider network to bring up an instance with the command: openstack server create --flavor m1.tiny --image cirros034 --nic net-id=4463e4a7-3b06-46d9-b24f-3e2e7867ee96 --security-group=5cf380e5-efb3-48b3-b8e9-095b1ebd817d provider-instance

the instance fails to be instantiated because the network cannot be deployed.

I noticed two points from the neutron-linuxbridge-agent.log file at the compute node (the logs at the controller seem fine):

1) ERROR neutron.plugins.ml2.drivers.agent._common_agent pyroute2.netlink.exceptions.NetlinkError: (13, 'Permission denied')

2) INFO neutron.plugins.ml2.drivers.agent._common_agent [req-816902d4-6581-49c1-939a-6ea69b437c99 - - - - -] Linux bridge agent Agent out of sync with plugin!  -- not sure if this one is a problem.

One part that i am not sure is the following configuration since i am on ubuntu 18 and not ubuntu 16:

# The provider network interface
auto INTERFACE_NAME
iface INTERFACE_NAME inet manual
up ip link set dev $IFACE up
down ip link set dev $IFACE down

I did not include this part in my file since its ubuntu 18, and netplan does not have an equivalent (i think) option. I have this netplan config

   enp0s8: --> mgmt
      dhcp4: false
      addresses: [10.0.0.31/24]
      gateway4: 10.0.0.1
      nameservers:
          addresses: [8.8.8.8, 8.8.4.4]
    enp0s9: --> provider
      dhcp4: false

any advice?

all the best,

Pavlos Basaras