Forwards route advertisements received from the external BGP router throughout the internal network.

• A. iBGP
• B. eBGP
• C. OSPF
• D. RIP

Answer: (A)

Inside an autonomous system, routes learned from an external BGP neighbor are distributed using iBGP. When the external BGP router advertises prefixes into your AS, those same prefixes are propagated to other internal routers via iBGP sessions. This is how the internal network learns about routes from outside the AS without using another exterior pathway. It’s important to note that iBGP requires careful topology (often a full mesh or a route reflector) because iBGP does not re-advertise routes learned from one iBGP peer to another. Also, the next-hop for eBGP-learned routes remains the external neighbor, which may require next-hop-self adjustments to reach all internal peers. This is why the best fit for forwarding external route advertisements throughout the internal network is iBGP.