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BGP path attributes — list the 6 well-known mandatory ones.

Per RFC 4271: AS_PATH, NEXT_HOP, ORIGIN, LOCAL_PREF (well-known discretionary, only for iBGP), ATOMIC_AGGREGATE (well-known discretionary), MED (optional non-transitive). Path selection order: Highest Weight (Cisco-only) → Highest LOCAL_PREF → Locally Originated → Shortest AS_PATH → Lowest ORIGIN → Lowest MED → eBGP over iBGP → Lowest IGP metric to next-hop → Oldest Route → Lowest Router-ID. Memorising this order is a CCNP / CCIE benchmark question.
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