BGP Attribute - ORIGIN

ORIGIN is a well-known mandatory attribute that specifies the origin of the routing update. 

There are 3 values : 

• i - Iternal/IGP - The route originated in an IGP. The NLRI was learn from a protocol internal to the originating AS. IP subnet is injected using network or aggregate command
• e - EGP - The route was learned from EGP (Exterior Gateway Protocol) which is not used anymore
• ? - Incomplete - The route was redistributed into BGP. The NLRI was learned by some other means. There is no way to determine the original source of the route.

 i < e < ? - lower is better !

BGP router will always prefer "i" routes, next "e" routes and "?" routes.