BGP

Aggregation can replace several more-specific advertisements with one covering prefix. It reduces downstream table entries only where the specifics are actually suppressed and no alternative peer supplies them. The components need not fill the whole summary: advertising a sparse block also attracts traffic for its holes. Aggregation therefore combines a scaling decision with a reachability and ownership decision. ...

BGP exchanges reachability between independently operated networks, but there is no single authoritative Internet forwarding table. Each router learns a policy-filtered view, chooses routes, and attempts to install usable next hops. Two routers can legitimately select different paths to the same prefix. Understanding BGP means separating announcements, selection policy, and packet forwarding rather than treating them as one universal answer. ...