When using neutron commands (e.g. net-list net-create) on the controller node, I get the following error:

Unable to establish connection to http://controller:9696/v2.0/networks.json: HTTPConnectionPool(host='controller', port=9696): Max retries exceeded with url: /v2.0/networks.json (Caused by NewConnectionError('<requests.packages.urllib3.connection.HTTPConnection object at 0x7fb507c2a210>: Failed to establish a new connection: [Errno 111] Connection refused',))

When I check the neutron-server.log, I get the following error:

ERROR neutron ProgrammingError: (pymysql.err.ProgrammingError) (1146, u"Table 'neutron.ml2_gre_allocations' doesn't exist") [SQL: u'SELECT ml2_gre_allocations.gre_id AS ml2_gre_allocations_gre_id, ml2_gre_allocations.allocated AS ml2_gre_allocations_allocated \nFROM ml2_gre_allocations FOR UPDATE']

Can somebody please guide me on how to solve this issue?