_______ is a connected group of one or more IP prefixes run by one or more network operators which has a SINGLE and CLEARLY DEFINED routing policy.

• A. Autonomous System
• B. Domain
• C. Subnet
• D. VLAN

Answer: (A)

An Autonomous System is a connected group of one or more IP prefixes operated by one or more network operators that share a single, clearly defined routing policy. This concept matters because it defines the boundary where internal routing decisions are controlled and how those prefixes are advertised to other networks using BGP. The unified routing policy across all prefixes in the AS ensures consistent behavior when exchanging routes with external networks, which is what routing decisions and inter-domain reachability hinge on.

Other concepts don’t fit this description: a domain is a naming realm used in DNS, not a routing boundary for prefixes across operators; a subnet is a single block of addresses within one network, not a collection of prefixes across multiple operators with a unified policy; a VLAN is a Layer 2 network segmentation, which operates within a local broadcast domain rather than governing inter-domain routing.