By default packstack --allinone does ML2&OVS&VXLAN setup.

I would just  plugged in one inexpensive card like  Realtek 8169 (or whichever detectable by yours OS to avoid driver compilation and install ) and make it OVS port of OVS Bridge br-ex, the last on should have IP on external network and should  exist for inbound&outbound Internet connectivity.

An other option pick up answer file from http://bderzhavets.blogspot.com/2015/... (ML2&OVS&VLAN Setup)

Update it for single host and tune as you need CONFIG_NEUTRON_ML2_VLAN_RANGES=physnet1:1000:1005
My guess is that 1000 and 1005 should be replaced by yours VLAN IDs.Then create external net of VLAN type with VLAN ID required. If yours external network has VLAN type, then only last option would have chance to work.