Which routing-instance type allows the sharing of interface routes and the support features used in source-based routing?

The correct choice relates to the concept of routing instances that are designed to facilitate advanced routing functions, including features such as source-based routing. The routing-instance type that allows for the sharing of interface routes while also supporting source-based routing is indeed the forwarding routing instance.

Forwarding instances are characterized by their ability to manage and segregate routing information, which enables complex traffic handling as per specific requirements or policies. This is essential for environments where different routing behaviors are necessary based on the source of the traffic, allowing for more granular control over routing decisions. In multiple scenarios, like when working with traffic from different customers or applications that necessitate distinct routing paths regardless of the destination, forwarding instances become particularly useful.

Other routing instance types like virtual-router and vrf (Virtual Routing and Forwarding) serve different purposes. Virtual-routers typically do not provide the same degree of flexibility for interface route sharing needed for source-based routing. VRF instances, while allowing multiple routing tables to coexist on the same device, are primarily focused on isolating traffic rather than enabling the specific sharing of interface routes.

Multi-instance can refer to situations where multiple instances of the same protocol or routing instance are allowed. Still, it does not specifically cater to the needs outlined in the question regarding routing