HP Aruba Certified Professional - Campus Access HPE7-A06 Question # 4 Topic 1 Discussion

The goal is to make the adjacent router prefer routes exported by AGG-SW2 over AGG-SW1 for iBGP and eBGP routes to AS65000. Both switches use a route-map BGP-EXPORT with an ip-prefix list local-export. BGP path selection uses attributes like local preference, AS path length, and metric to determine the preferred route.

Analysis of Options:

Option A:Setting local-preference 200 affects iBGP route selection within the same AS but has no impact on eBGP peers (external AS65000), as local preference is not advertised externally.

Option B:Prepending the AS path with 65345 65345 65345 65345 increases the AS path length for routes exported by AGG-SW1, making them less preferred by the adjacent router (both iBGP and eBGP peers) compared to AGG-SW2’s routes, which have a shorter AS path.

Option C:Setting metric 200 affects the MED (Multi-Exit Discriminator), which is used for eBGP route selection within the same AS but is less influential than AS path length and not applicable for iBGP.

Option D:Incorrect syntax (set as-path without prepend) and does not achieve the desired effect.

Why Option B is Correct:BGP route selection prioritizes the shortest AS path for both iBGP and eBGP. By prepending AS 65345 multiple times to AGG-SW1’s exported routes, AGG-SW1’s routes appear less attractive due to a longer AS path, causing the adjacent router to prefer AGG-SW2’s routes. This is a standard BGP traffic engineering technique.

Relevance to Certification Objectives:

Routing (16%):Involves designing and troubleshooting BGP routing topologies, including manipulating path attributes like AS path.

Troubleshooting (10%):Includes remediating BGP routing issues by adjusting route-maps.