You have configured an aggregate route for prefix 10.

The 10.20.0.0/22 aggregate covers the four /24 blocks 10.20.0.0/24 through 10.20.3.0/24, but only the first three of those (10.20.0.0/24, 10.20.1.0/24, and 10.20.2.0/24) are configured and present as active contributing routes; 10.20.3.0/24, the block containing the destination address 10.20.3.100, has no corresponding contributing route in this configuration. Because no more-specific route exists for 10.20.3.100, the longest-match lookup falls through the missing /24 and matches only the broader /22 aggregate itself. By default, when Junos installs an aggregate route, it assigns that route a reject next hop rather than any usable forwarding next hop; this is a deliberate design choice so that traffic destined for gaps within an advertised summary block — gaps where no real, more-specific path actually exists — is not blindly forwarded toward whatever next hop happens to belong to one of the unrelated contributing routes. A reject next hop causes the router to drop the packet and generate and return an ICMP destination-unreachable message to the originating source, explicitly informing it that no path exists, which is functionally and behaviorally distinct from a silent discard next hop that would drop the packet without any such notification. Aggregate routes never adopt or forward through any single contributing route's next hop, which rules out the two forwarding-based answer choices entirely. Reference topics: Junos Enterprise Routing – Protocol Independent Routing, Default Reject Next Hop for Aggregate Routes.