Which protocol forwards route advertisements received from the external BGP router throughout the internal network?

The correct answer is Internal Border Gateway Protocol (iBGP). This protocol is specifically designed to distribute routing information within an autonomous system (AS). In scenarios where external BGP routers receive route advertisements from outside the AS, iBGP is tasked with forwarding these advertisements to other internal routers. This ensures that all routers within the AS have consistent routing information derived from the external sources.

The functionality of iBGP is crucial in maintaining a coherent routing strategy in large networks where multiple routers need to operate seamlessly. By utilizing iBGP, network administrators can make sure that all internal routers can effectively communicate routing updates and maintain a unified view of the network topology.

In contrast, other options such as Virtual Network Computing (VNC), Domain Name System (DNS), and Remote Desktop Protocol (RDP) do not serve the purpose of forwarding routing advertisements. VNC is used for remote graphical desktop sharing, DNS translates domain names into IP addresses, and RDP is a protocol for remote desktop connections. None of these protocols involve the routing processes that iBGP is specifically designed to handle.