Border Gateway Protocol reduces the need for manual route configuration on routers because it is a dynamic routing protocol, and automatically learns routes between sites that are connected by using site-to-site VPN connections. In Windows Server 2012 R2, the RRAS Multitenant Gateway supports BGP, and allows you to provide dynamic routing for your tenants who are using routers that also support BGP.
The BGP overview topic, at http://technet.microsoft.com/en-us/library/dn614183.aspx, provides information on BGP features as well as the BGP supported deployment topologies, including the following:
For more information about the RRAS Multitenant Gateway, see the blog post New! Windows Server 2012 R2 RRAS Multitenant Gateway Deployment Guide at http://blogs.technet.com/b/wsnetdoc/archive/2014/03/26/new-windows-server-2012-r2-rras-multitenant-gateway-deployment-guide.aspx