No Internet in Image

[cccdemon]

Version Packer Latest.

What i try: Creating a Dockercontainer - which uses Packer to create a KVM/qemu Image.
So far so good.
Everything works fine, but if the build KVM Image tries to access the Internet it fails (while Build is on going)

Packer is able to connect via SSH and doing so stuff, if packer tries to update the created Image, no internetconnection is given.

Just to understand me correct:
We use this docker/packer image to create qemu images.
We dont generate the Dockerfile with packer!