When not to use BGP?

• A. BGP is only for experimental networks
• B. Sufficient memory and CPU power on edge routers
• C. Your routing policy matches the ISP
• D. A single connection to the internet or another AS (use a default route instead)

Answer: (D)

The situation to skip BGP is when you have just a single connection to the Internet (or to one other AS) and a default route is sufficient for reachability. BGP is designed for interdomain routing with multiple paths and policy-based decisions across many peers. It shines when you need control over path selection, traffic engineering, or redundancy with several upstreams. But all that complexity comes with overhead: BGP keeps routing state, processes frequent updates, and uses memory and CPU on your edge routers. If you only have one upstream and you don’t need to influence inbound or outbound traffic beyond a default path, using a default route (or the provider’s default) keeps things simple and resource-efficient.

Other options describe common reasons to use BGP or requirements that enable it (production use, policy control, adequate hardware). They aren’t reasons to avoid BGP, so the best fit is the single-connection scenario with a default route.