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

Question

Options

• AEGP
• BAS
• CMED
• DLOCAL_PREF

• A
  78% (51)
• B
  5% (3)
• C
  14% (9)
• D
  3% (2)

Explanation

Option A (EGP) is correct because the BGP Origin attribute has exactly three possible values in preference order: IGP (most preferred), EGP (second), and Incomplete (least preferred). The blank in the sequence "(), IGP, Incomplete" represents EGP, the middle value - routes learned via the older Exterior Gateway Protocol carry this attribute and are preferred over Incomplete but not over IGP.

Option B (AS) is wrong because AS refers to Autonomous System, which is relevant to the AS_PATH attribute, not the Origin attribute. Option C (MED) is wrong because MED (Multi-Exit Discriminator) is an entirely separate BGP attribute used to influence which entry point into an AS is preferred. Option D (LOCAL_PREF) is wrong because LOCAL_PREF is another distinct BGP attribute used within an AS to prefer outbound paths, and it is evaluated before Origin in the BGP decision process.

Memory tip: Think of the Origin values as a trust ladder - IGP means the route came from inside your own network (most trustworthy), EGP means it came from a now-obsolete external protocol (somewhat trustworthy), and Incomplete means the origin is unknown, typically from redistribution (least trustworthy). The order IGP > EGP > Incomplete reflects decreasing certainty about where the route originated.

No community discussion yet for this question.