In Junos OS, a BGP route is marked as "hidden" when it fails the route validation process and cannot be installed as an active route in the forwarding table (e.g., inet.0). The most common reason for a route to be hidden is that the BGP next-hop address is not resolvable. This means there is no active route in the routing table that can be used to reach the BGP next hop. The route is kept in the BGP routing table but is not considered for path selection or forwarding until the next hop becomes reachable.

A. Load balancing (ECMP) applies to multiple valid, active paths to a destination; it does not cause a route to become hidden.

B. Having too many hops would typically result in an AS path loop, causing the route to be rejected, not hidden due to next-hop validation.

D. If another route with a better metric (e.g., lower administrative distance) were selected, the BGP route would be marked "Inactive," not "Hidden."

1. Juniper Networks Documentation

"Junos OS Routing Protocols Library for Routing Devices"

section "Troubleshooting BGP". It explains

"A hidden route is a route that is not installed in the forwarding table because the next hop is unreachable."

2. Juniper Networks Knowledge Base

Article KB16138

"BGP routes are hidden and not active in the routing table". The primary cause listed is: "The BGP next-hop for the route is not reachable."