Security mechanisms such as firewalls commonly deployed throughout the Internet present serious obstacles to basic usage of Mobile IP. In this paper we describe how IP security mechanisms can be integrated with Mobile IP to create a mobile VPN. In this context, this work describes a prototype implementation of an integrated environment for secure, inter-domain, mobile communications for an existing corporate-like intranet of a public authority. In this paper the particular architecture of the deployment scenario and the implementation of the solution are described.