Retained Invalid Routes Can Suppress Route Discovery in ns-3 AODV

Routing entries can influence route discovery even after their forwarding paths have failed. We study a loop-prevention guard in ns-3.47 Ad hoc On-Demand Distance Vector (AODV) routing that suppresses a request when its sender matches the next hop of an existing destination entry. Retained INVALID entries can trigger this guard. In a four-node counterexample formed through ordinary protocol events, exempting only INVALID entries changes main-flow delivery from 0/95 to 95/95 packets, with a 14.5 ms first-arrival wait. A 24-run matrix separates retention from deletion, cold start, and a second topology. Isolated request-handler tests confirm the branch boundary, while temporal regressions distinguish the targeted exemption from removing the protection entirely: a constructed reverse-dependence test produces an active route cycle and packet return only without the guard. Across six 25-node environments with 5985 offered packets each, delivery improves in four, remains unchanged in one, and decreases by 56 packets in one. The negative case localizes losses to address resolution on a shared path prefix. The study identifies a state-dependent discovery failure and shows why its local repair must be assessed together with protective checks and network-level effects.