City public-works must stop a stub clinic from advertising a learned default route into the county core. Which control best prevents that unwanted advertisement?
Select an answer to reveal the explanation.
Short Explanation
Filters are the tollbooth facing the clinic: defaults don’t get a ticket into the county core. Prefix-lists or distribute-lists on the advertisement path stop the leak at the border. Speeding hellos or flipping VTP won’t police routes.
Full Explanation
Route filtering with prefix-lists, distribute-lists, or route-maps prevents a stub from advertising unwanted prefixes such as a default into the core. Filtering should sit on the redistribution or routing-update path between clinic and core. Hello timers affect adjacency liveliness rather than prefix policy, and PortFast or VTP cannot filter IP route advertisements. Combine stub design such as OSPF stub areas or EIGRP stub with explicit filters for defense in depth.