A large campus EIGRP network suffers SIA events and slow convergence because every remote site receives queries for every lost route, has many low-speed spoke routers, and needs to preserve optimal summarization at distribution. Which EIGRP query scoping design with stub routers and summarization best limits the impact?

The correct design works because EIGRP stub on low-speed remote spokes signals they are non-transit and should not be queried for lost routes, which stops campus-wide query flooding and SIA timers, while summarization at distribution creates a clean aggregation boundary that further limits query range, shrinks topology tables, and preserves optimal policy control. Advertising full topology from stub spokes without any summarization is common when visibility is prioritized, but it fails here because every specific prefix remains vulnerable to queries and large updates, so constrained spokes still suffer slow convergence and SIA risk despite stub status. Making distribution routers stub with summarization is used to protect a core from distribution instability, but it fails by directionality because the distribution layer must remain transit-capable, and stubbing it breaks optimal forwarding and does not shield edge spokes from inbound queries. Summarizing only at the spoke access layer is legitimate for reducing outbound advertisements, but it fails the requirement for optimal distribution summarization because it provides no central aggregation point, complicating policy and leaving core queries unbounded. For the exam, remember stub limits queries but does not auto-summarize, both must be explicitly configured. Practically, confirm stub neighbor flags, Null0 summary routes, and reduced SIA queries with show and debug validation.