Default Master Routing Instance

C

The default master routing instance is a special routing instance in Junos OS that is used to manage the device's default routing table. This routing instance contains all the routes that the device uses to forward traffic that is not explicitly defined in another routing instance.

Regarding the statement options provided, we can break down each answer and determine which one is true:

A. All IPv4 routes in the master routing instance are shared with user-defined routing instances. This statement is incorrect. While the master routing instance contains all the IPv4 routes for the device, it does not share them with user-defined routing instances by default.

B. Interface routes in the master routing instance are shared with user-defined routing instances. This statement is incorrect. Interface routes in the master routing instance are not shared with user-defined routing instances by default.

C. Routes in the master routing instance are not shared with user-defined routing instances. This statement is true. By default, routes in the master routing instance are not shared with user-defined routing instances.

D. All routes in the master routing instance are shared with user-defined routing instances. This statement is incorrect. By default, all routes in the master routing instance are not shared with user-defined routing instances.

In conclusion, option C is the correct answer. The routes in the master routing instance are not shared with user-defined routing instances by default. However, it is possible to share specific routes between routing instances using routing protocols or static routes.