In Junos OS, astatic routeis a manually configured entry in the routing table. Unlike dynamic routes, which have built-in timers and aging mechanisms, static routes are generally "permanent" as long as their conditions for validity are met.
1. Manual Removal (Option A):
Since static routes are explicitly defined by the administrator, the most direct way to remove one is through a configuration change. Using the delete routing-options static route command followed by a commit will immediately remove the route from the Routing Information Base (RIB).
2. Next-Hop Reachability (Option B):
For a static route to be "active" and installed in the forwarding table, itsnext-hop must be reachable. If a static route points to a specific physical interface or an IP address on a local segment, and thatoutbound interface becomes unavailable(e.g., the link goes "Down"), the Junos kernel detects that the next-hop is no longer viable. Consequently, the route is marked as "hidden" or "inactive" and is removed from the active forwarding table to prevent traffic from being black-holed.
Why other options are incorrect:
Aging (Option C):Static routes do not have an expiration timer based on traffic. Even if no packet is sent for years, the route remains as long as the interface is up.
Remote Reachability (Option D):Standard static routes only track the status of the local interface or the immediate next-hop. They do not possess "end-to-end" visibility. If a host two hops away fails, the local router has no way of knowing this via the static route itself. To achieve this level of tracking, features likeRPM (Real-time Performance Monitoring)orBFD (Bidirectional Forwarding Detection)must be linked to the static route.
