Sometimes, Tunnel I/F is not created in L2GW node after network / subnet / GATEWAY / CONNECTION creation. Logical Switch is created successfully.
This happens both in OVS HWVTEP Emulator and HWVTEP environment.

We found the following transaction was issued by checking L2GW Node OVSDB transaction log.

2018-02-01T05:54:57.677Z|00379|jsonrpc|DBG|tcp:172.16.1.30:6640: received request, method="transact", params=["hardware_vtep",{"uuid-name":"PhysicalLocator_Random_184830d8870c49139ecc278d281236a9","table":"Physical_Locator","op":"insert","row":{"dst_ip":"10.0.0.10","encapsulation_type":"vxlan_over_ipv4"}},{"where":[["name","==","ocata-l2gw1"]],"table":"Physical_Switch","op":"update","row":{"tunnel_ips":["set",["10.0.0.50"]]}},{"comment":"Physical Switch: Updating ocata-l2gw1","op":"comment"},{"uuid-name":"LogicalSwitch_e1ed1310_e35b_4a97_bf3e_cec8b82b6ba6","table":"Logical_Switch","op":"insert","row":{"name":"e1ed1310-e35b-4a97-bf3e-cec8b82b6ba6","tunnel_key":["set",[1038]],"replication_mode":["set",["source_node"]]}},{"comment":"Logical Switch: Creating e1ed1310-e35b-4a97-bf3e-cec8b82b6ba6","op":"comment"},{"where":[["name","==","patch-vlan"]],"table":"Physical_Port","op":"update","row":{"vlan_bindings":["map",[[1111,["named-uuid","LogicalSwitch_e1ed1310_e35b_4a97_bf3e_cec8b82b6ba6"]]]],"name":"patch-vlan"}},{"comment":"Physical Port: Updating patch-vlan","op":"comment"}], id="11677f02-5c83-45d9-9c54-131b079d3e69"
2018-02-01T05:54:57.677Z|00381|jsonrpc|DBG|tcp:172.16.1.30:6640: send reply, result=[{"uuid":["uuid","24356528-b515-40ca-9e3d-a37f101a95e2"]},{"count":1},{},{"uuid":["uuid","f38b7204-14a5-4f04-80ad-9cb45e83d267"]},{},{"count":1},{}], id="11677f02-5c83-45d9-9c54-131b079d3e69"

By using ovsdb-client command, we tried to execute this transaction to OVSDB ( not connected to ODL), and found the PhysicalLocator for 10.0.0.10 was not registered.
Therefore, Tunnel I/F was not created.

1. ovsdb-client transact '
   ["hardware_vtep",
   {"uuid-name":"PhysicalLocator_Random_184830d8870c49139ecc278d281236a9","table":"Physical_Locator","op":"insert","row":{"dst_ip":"10.0.0.10","encapsulation_type":"vxlan_over_ipv4"}},
   {"where":[["name","==","ocata-l2gw1"]],"table":"Physical_Switch","op":"update","row":{"tunnel_ips":["set",["10.0.0.50"]]}},
   {"comment":"Physical Switch: Updating ocata-l2gw1","op":"comment"},
   {"uuid-name":"LogicalSwitch_e1ed1310_e35b_4a97_bf3e_cec8b82b6ba6","table":"Logical_Switch","op":"insert","row":{"name":"e1ed1310-e35b-4a97-bf3e-cec8b82b6ba6","tunnel_key":["set",[1038]],"replication_mode":["set",["source_node"]]}},
   {"comment":"Logical Switch: Creating e1ed1310-e35b-4a97-bf3e-cec8b82b6ba6","op":"comment"},
   {"where":[["name","==","patch-vlan"]],"table":"Physical_Port","op":"update","row":{"vlan_bindings":["map",[[1111,["named-uuid","LogicalSwitch_e1ed1310_e35b_4a97_bf3e_cec8b82b6ba6"]]]],"name":"patch-vlan"}},
   {"comment":"Physical Port: Updating patch-vlan","op":"comment"}
   ]'
   [{"uuid":["uuid","777d4230-adc0-4388-8706-717d29b80ed2"]},{"count":1},{},{"uuid":["uuid","4407fc13-01ff-43fa-a09b-632c5b4e3d8b"]},{},{"count":1},{}]

After tried several times, we found that for PhysicalLocator registeration, PhysicalLocator_Set and MAC tables referencing PhysicalLocator_Set (such as Mcast_Macs_Remote) need to be registered at the same time.

○Reproduction steps:
1. Start L2GW Node
2. Create network / subnet / GATEWAY / CONNECTION