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 to i (IGP).
* Option B: Incorrect. Routes learned from EGP have the Origin attribute set to e (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.
References:
* HCIA-Datacom Study Guide, Chapter: BGP Attributes
* Huawei BGP Attribute Comparison