Which protocol is used for internal propagation of BGP routes within an enterprise?

Which protocol is used for internal propagation of BGP routes within an enterprise?

• A. OSPF
• B. Internal Border Gateway Protocol (iBGP)
• C. RIP
• D. DNS

Answer: (B)

Internal BGP, or iBGP, is used to propagate BGP routes inside an organization. BGP distinguishes external routing between different autonomous systems (eBGP) from internal routing within the same autonomous system (iBGP). When routes are learned from external peers, iBGP shares those routes with other internal neighbors so the entire AS can reach those destinations. To ensure all internal routers know the complete set of routes, iBGP sessions are typically fully meshed or you use route reflectors. OSPF and RIP are interior gateway protocols for general internal routing of IP networks, not for spreading BGP routes. DNS is unrelated to routing protocol propagation. So the best fit for internal propagation of BGP routes within an enterprise is iBGP.