Why does a BGP router form neighbor relationships with a limited number of peers?

• A. Because the router can't handle communications from a large number of AS
• B. Because BGP requires at least 100 peers
• C. Because neighbors must be in the same AS
• D. Because of license constraints

Answer: (A)

BGP neighbor relationships are limited by the router’s ability to maintain control-plane state for each session. Every neighbor creates a separate TCP session and BGP session state, which consumes CPU, memory for routing tables and per-session data, and bandwidth to send and process updates. As you add more peers, the router must handle more sessions, more updates, and more churn, which can slow convergence and degrade performance. That’s why operators cap the number of peers and use mechanisms like route reflectors or confederations to scale without overwhelming the router. The other statements don’t fit: BGP doesn’t require a minimum number of peers, neighbors don’t all have to be in the same AS for every session, and licensing is not the fundamental reason for limiting peers.