What is the purpose of BGP confederations?

• A. Split an AS into sub-ASs to scale iBGP
• B. Encrypt all BGP updates
• C. Decrease route visibility
• D. Merge multiple AS into one

Answer: (A)

BGP confederations are a way to scale routing inside a very large AS by dividing it into multiple sub-ASes while presenting a single AS to the outside world. In a big network, keeping an iBGP full mesh among all internal routers becomes complex and heavy. By splitting into sub-ASes, each sub-AS handles its own iBGP, and the connections between sub-ASes can use EBGP, which reduces the number of iBGP sessions the network must maintain. This keeps routing policy and convergence manageable without exposing multiple AS numbers externally. Encrypting BGP updates, reducing route visibility, or merging ASes aren’t what confederations are designed to do.