BGP prefers the route with the best Origin attribute value. The value of the Origin attribute is: EGP, IGP, ().

Question

Options

• Aincomplete
• Bcomplete
• Cunknown
• Dlocal

• A
  77% (36)
• B
  6% (3)
• C
  13% (6)
• D
  4% (2)

Explanation

Option A is correct because BGP's Origin attribute has exactly three defined values: IGP, EGP, and Incomplete - and "incomplete" is the missing third value in the sequence given. Incomplete (represented by "?" in routing tables) indicates that the route's origin cannot be determined precisely, typically because it was redistributed into BGP from another protocol or learned via a static route. Options B ("complete"), C ("unknown"), and D ("local") are all fabricated values that do not exist in the BGP specification - BGP RFC 4271 defines only IGP, EGP, and Incomplete as valid Origin codes. For BGP path selection, IGP is most preferred, EGP is second, and Incomplete is least preferred when all other attributes are equal.

Memory tip: Use the mnemonic "I Eat Incomplete meals" - IGP, EGP, Incomplete - to remember both the three valid values and their preference order from best to worst.

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