Comment 8 for bug 1675778

So the difference between nets 1 and 2 is that for net 1 dhcp port is first created for one ipv4 subnet:

2017-03-30 05:12:33.660 29848 DEBUG neutron.api.rpc.handlers.dhcp_rpc [req-e099424a-10a2-48f3-ad99-67428a81cb3f - - - - -] Create dhcp port {u'port': {u'name': u'', u'admin_state_up': True, u'network_id': u'29d6752b-027a-4eb9-aa73-711eff1b58ca', u'tenant_id': u'0080fdf7aa774a11bb260f5b8129446c', u'fixed_ips': [{u'subnet_id': u'3f81f975-5718-4bdc-878c-614f22b1b783'}], u'device_id': u'dhcp5dbbf756-2249-5cb9-b9b4-259ca353b226-29d6752b-027a-4eb9-aa73-711eff1b58ca'}}

and then with the creation of ipv6 subnet the port is updated to have ipv6 ip:

2017-03-30 05:12:38.990 29848 DEBUG neutron.api.rpc.handlers.dhcp_rpc [req-bcd62396-0e9a-4f39-8bf7-e56f0588805c - - - - -] Update dhcp port {u'port': {u'network_id': u'29d6752b-027a-4eb9-aa73-711eff1b58ca', 'binding:host_id': u'node-2.test.domain.local', u'fixed_ips': [{u'subnet_id': u'3f81f975-5718-4bdc-878c-614f22b1b783', u'ip_address': u'192.168.100.2'}, {u'subnet_id': u'8363ac60-c30d-43dc-a1d1-3d39820602fd'}]}, 'id': u'2e3a5343-a995-498a-85d2-db686d119fab'}

for some reason no ipv6 address is not allocated and port is returned to dhcp agent with still one ipv4 ip: agent considers it as error (it is actually) and tries to resync.

for net2 dhcp port is created with ip allocation from both ipv4 and ipv6 subnets:

2017-03-30 05:12:42.999 29848 DEBUG neutron.api.rpc.handlers.dhcp_rpc [req-fa681e8c-6831-4d7f-aec0-f42985c6b5f6 - - - - -] Create dhcp port {u'port': {u'name': u'', u'admin_state_up': True, u'network_id': u'4bb359f3-1800-4695-b8a9-e61a381052b7', u'tenant_id': u'0080fdf7aa774a11bb260f5b8129446c', u'fixed_ips': [{u'subnet_id': u'a22cd89d-831d-4ad7-9e1d-aab89f2fb9ac'}, {u'subnet_id': u'1f6f7b07-8947-434f-855b-5f9dec4417a1'}], u'device_id': u'dhcp5dbbf756-2249-5cb9-b9b4-259ca353b226-4bb359f3-1800-4695-b8a9-e61a381052b7'}}

and everything is ok.

Need to figure out why server can't allocate ipv6 address for dhcp port of net1