A company uses BGP to connect with the ISP on the enterprise network and wants to improve performance due to the increasing number of iBGP peers. Which two design solutions address the iBGP full…

Question

Options

• Aroute reflectors
• Bconfederations
• CAS path prepending
• Dcommunities
• Econditional advertising

• A
  84% (27)
• C
  9% (3)
• D
  3% (1)
• E
  3% (1)

Explanation

iBGP requires a full mesh by default because iBGP routers do not re-advertise routes learned from one iBGP peer to another iBGP peer (split-horizon rule). With n peers, a full mesh requires n*(n-1)/2 sessions, which becomes unmanageable at scale. A (Route reflectors) is correct: A route reflector (RR) re-advertises iBGP routes to its clients, eliminating the need for a full mesh among clients. Clients only need sessions with the RR. B (Confederations) is correct: Confederations divide a large AS into multiple sub-ASes. Within each sub-AS, a smaller full mesh (or RRs) is needed, and sub-ASes peer using eBGP-like rules with modified iBGP attributes. This dramatically reduces the total number of required sessions. C (AS path prepending) affects inbound traffic engineering, not iBGP scalability. D (Communities) are used for route tagging and policy, not for eliminating full mesh. E (Conditional advertising) controls when routes are advertised, not how iBGP sessions are structured.

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