Within an autonomous system, which session type is used to share routes between iBGP peers?

• A. eBGP
• B. iBGP
• C. OSPF
• D. IS-IS

Answer: (B)

This question tests how BGP distributes routes inside a single autonomous system. Internal BGP sessions connect routers within the same AS to share BGP reachability information. That’s the mechanism used to exchange routes between iBGP peers. It contrasts with external BGP, which handles routes between different ASes. OSPF and IS-IS are IGPs used for internal routing, not BGP session types. A useful nuance is that iBGP doesn’t automatically re-advertise routes learned from one iBGP neighbor to other iBGP neighbors unless you have a full mesh, or use route reflectors or confederations, to prevent routing loops.