Vyatta virtual router - alternative?

I’m going through the Network Pentesting module for Penterster Academy, and the instructor starts by walking through the download of the Vyatta iso and installation on Virtualbox.

Vyatta has since been acquired by another company and there doesn’t seem to be an available download of the iso file…does anyone else have a free edition of a virtual router software that can be considered an alternative to Vyatta?

Thanks in advance!