Please,post (as update to question):

    1. /etc/neutron/plugins/ml2/ml2_conf.ini
    2. /var/log/neutron/openvswitch-agent.log
    Output :
    $ neutron agent-list

   Mistake in /etc/neutron/plugins/ml2/ml2_conf.ini fixed

There can be many reasons for this. Share the logs of the service "openvswitch-agent.log".

I also has the same problem today. And I totally solve the problem. I will leave here my solution as a reference.

The first very thing to aware of is that we should not leave any space for each line in a configure file of openstack.

For example, the conig. file: ml2_conf.ini when installing the openvswitch on network and compute1 node: if we just uncomment a line like this:

   tenant_network_types = gre

Then we will end up with a problem. And we will find that when we restart a service, soonly we will find it stop after few seconds.

So we should not only uncomment a line, but also remove the space like this:

tenant_network_types

For openvswitch problem like this thread, there's an additional problem that we may found in the log file:/var/log/neutron/openvswitch-agent.log

It is a problem due to the neutron-rootwrap.

So the solution for this could be solved by:

cp -a /usr/lib/python2.7/dist-packages/oslo/rootwarp /usr/local/lib/python2.7/dist-packages/oslo

For the compute1 node, we should mkdir /usr/local/lib/python2.7/dist-packages/oslo before the above cp