Validate PIM-DM flood-and-prune operation and consider PIM-SM if receiver distribution is sparse. This is a legitimate response to the different issue of PIM-DM flood and prune behavior, but it does not correct the specific RIB-to-FIB forwarding discrepancy condition reported. The relevant technical distinction is: The routing information base selects routes while the forwarding information base programs actual packet forwarding.

Restrict redistribution using explicit route policies and route tags to prevent readvertising imported prefixes. This is a legitimate response to the different issue of Route import feedback loop, but it does not correct the specific RIB-to-FIB forwarding discrepancy condition reported. The relevant technical distinction is: The routing information base selects routes while the forwarding information base programs actual packet forwarding.

Select the longest matching destination prefix first, and compare route preference among eligible routes for the same prefix. This is a legitimate response to the different issue of Longest-prefix and route preference, but it does not correct the specific RIB-to-FIB forwarding discrepancy condition reported. The relevant technical distinction is: The routing information base selects routes while the forwarding information base programs actual packet forwarding.

The imported prefixes appear once with intended preference and do not reenter their originating protocol. That observation would support a separate case of Route import feedback loop, not verification of the reported RIB-to-FIB forwarding discrepancy. The relevant observable outcome here is: The route and forwarding entries agree and a packet trace takes the selected viable next hop.

Forwarding to a host inside the /25 follows the specific route while other addresses use the appropriate less-specific entry. That observation would support a separate case of Longest-prefix and route preference, not verification of the reported RIB-to-FIB forwarding discrepancy. The relevant observable outcome here is: The route and forwarding entries agree and a packet trace takes the selected viable next hop.

The adjacency leaves ExStart or Exchange and reaches Full with matching link MTU behavior. That observation would support a separate case of OSPF MTU stalls ExStart, not verification of the reported RIB-to-FIB forwarding discrepancy. The relevant observable outcome here is: The route and forwarding entries agree and a packet trace takes the selected viable next hop.

OSPF broadcast networks use a designated router to reduce adjacency and LSA exchange overhead. This explains Broadcast OSPF DR and BDR election, but not why the issue in this scenario occurs. The specific mechanism is: The routing information base selects routes while the forwarding information base programs actual packet forwarding.

IP forwarding uses longest-prefix match; protocol route preference decides among competing candidates for the same prefix. This explains Longest-prefix and route preference, but not why the issue in this scenario occurs. The specific mechanism is: The routing information base selects routes while the forwarding information base programs actual packet forwarding.

Uncontrolled mutual route import can form routing feedback loops and unstable route selection. This explains Route import feedback loop, but not why the issue in this scenario occurs. The specific mechanism is: The routing information base selects routes while the forwarding information base programs actual packet forwarding.

Applying the policy at the wrong routing role leaves external LSAs unchanged. This consequence is associated more directly with OSPF external summarization at ASBR. For the stated conditions the immediate exposure is: Treating a displayed RIB route as proof of working forwarding can prolong a blackhole.

Confusing the two selection stages can divert traffic to the wrong WAN gateway. This consequence is associated more directly with Longest-prefix and route preference. For the stated conditions the immediate exposure is: Treating a displayed RIB route as proof of working forwarding can prolong a blackhole.

Assuming a Hello neighbor alone provides a complete topology can create inconsistent routing decisions. This consequence is associated more directly with OSPF LSDB synchronization failure. For the stated conditions the immediate exposure is: Treating a displayed RIB route as proof of working forwarding can prolong a blackhole.

Trace protocol origin, import rules, tags, preferences and repeated route updates. This check would diagnose Route import feedback loop, but would not first isolate the described RIB-to-FIB forwarding discrepancy. Begin with: Inspect the Huawei IP routing table, FIB entries, adjacency resolution and a test flow.

Trace Type 7 advertisements, P-bit or translation selection and Type 5 LSAs outside the NSSA. This check would diagnose OSPF NSSA type-7 translation, but would not first isolate the described RIB-to-FIB forwarding discrepancy. Begin with: Inspect the Huawei IP routing table, FIB entries, adjacency resolution and a test flow.

Compare destination address, prefix lengths, active candidate routes and the FIB lookup. This check would diagnose Longest-prefix and route preference, but would not first isolate the described RIB-to-FIB forwarding discrepancy. Begin with: Inspect the Huawei IP routing table, FIB entries, adjacency resolution and a test flow.

Configure reviewed external route import on the intended ASBR and confirm Type 5 LSA propagation into eligible areas. This is a legitimate response to the different issue of OSPF type-5 external advertisement, but it does not correct the specific RIB-to-FIB forwarding discrepancy condition reported. The relevant technical distinction is: The routing information base selects routes while the forwarding information base programs actual packet forwarding.

Restrict redistribution using explicit route policies and route tags to prevent readvertising imported prefixes. This is a legitimate response to the different issue of Route import feedback loop, but it does not correct the specific RIB-to-FIB forwarding discrepancy condition reported. The relevant technical distinction is: The routing information base selects routes while the forwarding information base programs actual packet forwarding.

Select the longest matching destination prefix first, and compare route preference among eligible routes for the same prefix. This is a legitimate response to the different issue of Longest-prefix and route preference, but it does not correct the specific RIB-to-FIB forwarding discrepancy condition reported. The relevant technical distinction is: The routing information base selects routes while the forwarding information base programs actual packet forwarding.

Forwarding to a host inside the /25 follows the specific route while other addresses use the appropriate less-specific entry. That observation would support a separate case of Longest-prefix and route preference, not verification of the reported RIB-to-FIB forwarding discrepancy. The relevant observable outcome here is: The route and forwarding entries agree and a packet trace takes the selected viable next hop.

The imported prefixes appear once with intended preference and do not reenter their originating protocol. That observation would support a separate case of Route import feedback loop, not verification of the reported RIB-to-FIB forwarding discrepancy. The relevant observable outcome here is: The route and forwarding entries agree and a packet trace takes the selected viable next hop.

The peer relationship reaches the expected adjacency state and area routing updates arrive. That observation would support a separate case of OSPF area-ID mismatch, not verification of the reported RIB-to-FIB forwarding discrepancy. The relevant observable outcome here is: The route and forwarding entries agree and a packet trace takes the selected viable next hop.

BGP AS_PATH loop detection prevents a route from circulating back through an AS already in its path. This explains BGP AS_PATH loop detection, but not why the issue in this scenario occurs. The specific mechanism is: The routing information base selects routes while the forwarding information base programs actual packet forwarding.

IP forwarding uses longest-prefix match; protocol route preference decides among competing candidates for the same prefix. This explains Longest-prefix and route preference, but not why the issue in this scenario occurs. The specific mechanism is: The routing information base selects routes while the forwarding information base programs actual packet forwarding.

Uncontrolled mutual route import can form routing feedback loops and unstable route selection. This explains Route import feedback loop, but not why the issue in this scenario occurs. The specific mechanism is: The routing information base selects routes while the forwarding information base programs actual packet forwarding.

Confusing the two selection stages can divert traffic to the wrong WAN gateway. This consequence is associated more directly with Longest-prefix and route preference. For the stated conditions the immediate exposure is: Treating a displayed RIB route as proof of working forwarding can prolong a blackhole.

Shared credentials or bypassed NAC can grant former employees access to protected wireless networks. This consequence is associated more directly with WLAN 802.1X authentication and NAC. For the stated conditions the immediate exposure is: Treating a displayed RIB route as proof of working forwarding can prolong a blackhole.

Applying the policy at the wrong routing role leaves external LSAs unchanged. This consequence is associated more directly with OSPF external summarization at ASBR. For the stated conditions the immediate exposure is: Treating a displayed RIB route as proof of working forwarding can prolong a blackhole.

Inspect IGMP version, receiver reports, group address and installed source list. This check would diagnose IGMPv3 source-specific membership, but would not first isolate the described RIB-to-FIB forwarding discrepancy. Begin with: Inspect the Huawei IP routing table, FIB entries, adjacency resolution and a test flow.

Inspect neighbor phase, LSR retransmission lists, relevant LSAs and interface loss. This check would diagnose OSPF LSDB synchronization failure, but would not first isolate the described RIB-to-FIB forwarding discrepancy. Begin with: Inspect the Huawei IP routing table, FIB entries, adjacency resolution and a test flow.

Trace protocol origin, import rules, tags, preferences and repeated route updates. This check would diagnose Route import feedback loop, but would not first isolate the described RIB-to-FIB forwarding discrepancy. Begin with: Inspect the Huawei IP routing table, FIB entries, adjacency resolution and a test flow.