What is the hop-by-hop routing paradigm?

• A. BGP specifies that a router can advertise to its peers in neighboring AS only those routes that it uses
• B. BGP uses a full-mesh path across all ASes
• C. BGP does not consider policies when advertising routes
• D. BGP forwards traffic by specifying a global next-hop for all destinations

Answer: (A)

Hop-by-hop routing in BGP means each hop along the path makes its own forwarding decision and propagates only the routes it actually intends to use. A BGP speaker advertises routes to its neighboring ASes based on what it has selected as the best path and in line with its export policies. In practice, this keeps route advertisements aligned with local forwarding decisions and policies, rather than flooding every learned route. That’s why the statement that a router can advertise to its peers only those routes it uses is the best description.

The other ideas don’t fit: BGP doesn’t mandate a fixed full-mesh across all ASes (iBGP topologies can use route reflectors or confederations to avoid full mesh); policies do influence what gets advertised, so it’s not true that policies aren’t considered; and there isn’t a single global next-hop for all destinations—each route carries its own next-hop attribute, which is determined per route.