A provider configures a conditional advertisement so a backup prefix is advertised to a peer only when the primary prefix is withdrawn from the local routing table. Which behavior will you observe after configuring 'neighbor X advertise-map backup exist' correctly?

The neighbor X advertise-map backup exist command configures conditional advertisement. The exist keyword specifies that the route-map backup (which permits the backup prefix) will only be applied and advertised if the routes specified in a corresponding non-exist-map (which would typically reference the primary prefix) are not present in the BGP routing table. Therefore, the backup prefix is advertised only when the primary prefix is withdrawn. The backup prefix will not be advertised immediately because the exist keyword implies a condition based on the presence or absence of other routes. It's not solely dependent on IGP failures; BGP conditional advertisement operates on the BGP table. Lastly, advertise-map is used for outbound route filtering and manipulation, not inbound.