350-501 Question #241: Real Exam Question with Answer & Explanation

Question

Refer To the exhibit. Which BGP attribute should be manipulated to have CE1 use PE1 as the primary path to the Internet?

Options

• AThe weight attribute should be manipulated on PE1 on outbound routes advertised to CE1.
• BThe MED should be manipulated on CE1 on inbound routes from PE1.
• CThe local preference attribute should be manipulated on PE2 on inbound routes advertised to
• DThe origin of all routes should be modified on each router on inbound and outbound routes

Explanation

To have CE1 prefer PE1 as the primary path to the Internet, the BGP origin attribute can be manipulated such that routes advertised by PE1 to CE1 appear with a more preferred origin type than those from PE2.

Common mistakes.

• A. The Weight attribute is Cisco proprietary and strictly local to the router where it is configured; it is not advertised to other BGP neighbors, so manipulating it on PE1's outbound routes would not affect CE1's path selection.
• B. The MED attribute is typically used by an AS to influence how an external AS sends traffic into the local AS, or for influencing path selection among multiple exit points within the same AS, but manipulating it on CE1 for inbound routes is less common and a lower-priority attribute than origin in the decision process.
• C. The Local Preference attribute, typically configured on a router for inbound routes to affect its own path selection, if manipulated on PE2 for inbound routes, would primarily affect PE2's path choice, not directly CE1's preference for paths from PE1 to the Internet.

Concept tested. BGP path selection and origin attribute manipulation

Reference. https://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/13753-3.html

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