What describes full-mesh iBGP?

• A. By default, each BGP speaker is assumed to have a neighbor statement for all other iBGP speakers in the AS
• B. iBGP uses route reflectors by default
• C. Full mesh cannot be achieved in iBGP
• D. All iBGP peers are EBGP neighbors

Answer: (A)

In iBGP, to make sure every router in the same AS learns the same external routes, you typically need a full mesh: every iBGP speaker peers directly with every other iBGP speaker. This is important because iBGP does not re-advertise routes learned from one iBGP neighbor to other iBGP neighbors, so without direct iBGP connections between all pairs, some routers won’t see certain routes. The statement reflects this setup: by default, you configure a neighbor relationship between every pair of iBGP speakers in the AS, forming a full mesh. The other options don’t fit because route reflectors are optional tools to reduce the number of required iBGP sessions, full mesh can indeed be achieved in iBGP, and iBGP peers reside inside the same AS (EBGP peers are between different ASes).