How to model in TOSCA a link from my VNF to an external network (provider net)?

Hi,

I'm trying to create a simple TOSCA template to instantiate a VNF using VFC.
To model this i'm using the entity "tosca.nodes.nfv".

I'm able to create a VNF with a simple VDU, CP and a VL, upload it to VFC catalog and instantiate. 
Onap Private Network (VL)------------------> Cp ---> VDU

Now, what I would like to do is to connect my private network (VL) defined on
TOSCA template to an existent provider network.

Pretended:
Openstack Public Network -------------> Router ----------> Onap Private Network (VL)-------------> Cp ---> VDU

Is that possible to define into the template? and if yes how I can model that conection?

Summary Template:
VL:
properties:
...

CP:
requirements:
- virtual_binding: VDU
- virtual_link: VL

Vdu.Compute:
properties:
...
capabilities:
...

Thanks!