What is an external BGP neighbor?

• A. When BGP is running between routers in the same AS. The routers are usually directly connected
• B. When BGP is running between routers in different AS. The routers are usually directly connected to one another.
• C. When BGP runs over an internal network only
• D. When BGP uses IPv6 only

Answer: (B)

An external BGP neighbor is a BGP session with a peer in a different autonomous system. In BGP there are two scopes: eBGP across AS boundaries and iBGP inside the same AS. The term “external” highlights that routing information is exchanged between independent networks, carrying policies and AS-path data that identify the neighbor’s AS. Typically, eBGP sessions are formed over a directly connected link between the two routers, and the default behavior uses a TTL of 1 to reinforce that direct neighbor relationship. Internal BGP, by contrast, operates inside a single AS and can span multiple hops with more complex topology. The other options describe conditions that don’t capture the crossing of AS boundaries or overstate IPv6-only usage.