A company is multi homed to different service providers running BGP. Which action ensures that the company AS does not become a transit AS?

Question

Options

• ACreate a prefix list that matches the company prefix(es) and applies to both BGP neighbor
• BCreate a distribute list that filters all routes except the default route and applies to a single BGP
• CCreate a route map that matches the provider BGP communities and networks and applies to
• DCreate a distribute list that filters all routes except the default route and applies to both BGP

• A
  74% (34)
• B
  2% (1)
• C
  17% (8)
• D
  7% (3)

Explanation

A transit AS forwards traffic between two other ASes using its own infrastructure. To prevent this, you must ensure you advertise only your own prefixes to both upstream providers, not routes learned from one provider to the other. Creating a prefix list that permits only your company's own IP prefixes and applying it as an outbound filter on both BGP neighbor sessions (A) achieves this. Filtering inbound routes with a distribute list (B, D) controls what you accept but does not prevent you from re-advertising learned routes outbound. A route map matching provider BGP communities (C) is not a reliable or complete solution for preventing transit.

No community discussion yet for this question.