Which of the following statements regarding BGP route selection is TRUE?

Question

Options

• ALower local preference is preferred over higher local preference.
• BHigher MED is preferred over lower MED.
• CHigher origin code is preferred over lower origin code.
• DLower BGP router ID is preferred over higher BGP router ID.

• A
  2% (1)
• B
  5% (2)
• D
  93% (39)

Explanation

D is correct because when BGP has exhausted all other tiebreakers (weight, local preference, AS path length, origin, MED, eBGP vs iBGP, IGP metric), it selects the route from the neighbor with the lowest BGP Router ID (derived from the highest loopback IP, or highest physical IP if no loopback exists) - lowest wins at this final step.

Why the distractors are wrong:

• A is backwards - BGP prefers higher local preference (default 100; higher = more preferred).
• B is backwards - BGP prefers lower MED (Multi-Exit Discriminator); a lower MED signals a more preferred entry point.
• C is backwards - BGP prefers lower origin codes: IGP (i) < EGP (e) < Incomplete (?), so lower numeric value wins.

Memory tip: For BGP attributes, "higher is better" applies to Weight and Local Preference (both are locally significant and you want more), while "lower is better" applies to AS Path length, MED, and Router ID. Think of it as: local = high, external = low.

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