What is the correct EBGP path attribute list, ordered from most preferred to the least preferred, that the BGP best-path algorithm uses?

Question

Options

• Aweight, AS path, local preference, MED
• Bweight, local preference, AS path, MED
• Clocal preference, weight, AS path, MED
• Dlocal preference, weight MED, AS path

• A
  3% (1)
• B
  93% (28)
• D
  3% (1)

Explanation

BGP Best-Path Selection Explanation

Option B is correct because the BGP best-path algorithm evaluates attributes in this specific order: Weight (Cisco proprietary, highest value preferred) → Local Preference (highest value preferred) → AS Path (shortest path preferred) → MED (lowest value preferred). This sequence reflects the actual decision logic Cisco routers use when selecting the best path among multiple BGP routes.

Why the distractors are wrong:

• Option A incorrectly places AS Path before Local Preference - Local Preference is always evaluated before AS Path in the algorithm.
• Option C swaps Weight and Local Preference - Weight is always the first (highest priority) attribute checked, not Local Preference.
• Option D incorrectly places MED before AS Path - MED is only compared as a tiebreaker after AS Path has already been evaluated.

Memory Tip: Use the mnemonic "We Love AS MEDs" → Weight, Local Preference, AS Path, MED. Alternatively, remember the phrase "We Look At More Details" - the attributes generally move from locally significant (Weight, Local Pref) to externally significant (AS Path, MED), which reflects their scope in the network.

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