Went through a several-stage process; First, an overall assessment of my experience and ability to present a professional client-facing demeanor. Second, specific technical questions about experience from a senior recruiting engineer (subject matter expert). Third, questions from a account lead with detailed knowledge of the specific project engagement. Fourth, another discussion with the recruiting engineer over specific requirements of the project.
All phases were amiable, professional discussions with the first being the most relaxed and the final being the most technically in-depth. The final interview was virtually an oral skills test of network design.