What happens when a packet matches a static route with the next hop parameter set to reject?

When a packet matches a static route configured with the reject next-hop action, the Junos device performs two actions: it drops the packet and sends an ICMP "Destination Unreachable" message back to the source host. This behavior explicitly informs the source that the destination is unreachable, which is distinct from the discard action that drops the packet silently without any notification. The reject option is commonly used to enforce routing policies and provide immediate feedback about unreachable networks.

A. The system silently drops the packet.

This describes the discard next-hop action, not reject. Reject actively sends an ICMP notification.

B. An ICMP message is sent to the source and the packet is forwarded.

This is incorrect because the primary function of the reject action is to stop the packet from being forwarded.

D. The packet is forwarded and the packet is marked as rejected in the header.

This is incorrect. The packet is dropped, not forwarded, and there is no standard mechanism to "mark" a packet as rejected in its header for forwarding.

1. Juniper Networks TechLibrary, Junos OS Routing Protocols Library for Routing Devices: In the section describing static routing options, the reject next-hop is defined. It states, "If the routing device receives a packet for which the destination address matches a route that has reject as the next hop, the routing device drops (discards) the packet and sends an ICMP destination unreachable message to the source."

Source: Junos OS Routing Protocols Library for Routing Devices, "Static Route Options" section.

2. Juniper Networks TechLibrary, static (Protocols) Configuration Statement: The configuration guide for static routes explicitly lists the possible next-hop actions.

Source: static (Protocols) Statement Reference, under [edit routing-options static route destination-prefix]. The documentation for the reject option specifies: "Reject the packet and send an ICMP unreachable message."