Which term describes a single administrative domain with a unique routing policy?

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

Answer: (B)

A single administrative domain with its own routing policy is described by an autonomous system. In Internet routing, networks under one organization are grouped into Autonomous Systems to control how packets are forwarded between them. Each AS runs its own internal routing protocol to manage routes inside the domain and uses the exterior routing protocol BGP to exchange routes with other ASes. The policies—what routes to advertise, which paths to prefer, and which to filter—are defined at the AS level, so that consistent rules apply across all networks within that domain. Subnet refers to a subdivision of an IP network, not the overall administrative routing policy. VLAN is a logical segmentation within a single LAN, and Domain can be a broader or different concept that doesn’t specify a unique external routing policy.