Comprehensive and Detailed Step-by-Step Explanation:

Definition of the Origin Attribute:

The Origin attribute is a well-known mandatory attribute used to indicate the source of a route. It has three possible values:

i (IGP):The route was injected into BGP using the network command.

e (EGP):The route was learned from an EGP protocol (not commonly used now).

? (Incomplete):The route was redistributed into BGP from another routing protocol.

Analysis of Each Option:

Option A:Correct. When the network command is used, the Origin is set toi (IGP).

Option B:Incorrect. Routes learned from EGP have the Origin attribute set toe (EGP), not? (Incomplete).

Option C:Correct. BGP prefers routes with the Origin attribute in the order:IGP > EGP > Incomplete.

Option D:Correct. The Origin attribute is a well-known mandatory attribute.