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This option proposes: Inspect the destination address, matching installed prefixes, their mask lengths, route sources, next-hop resolution and the forwarding decision. It addresses the different topic Longest prefix match and route preferences, not the directly tested Network forwarding planes RIB versus FIB failure in the stated incident (During a maintenance cutover an operator sees a static route in configuration but a line-card forwarding inspection shows an unresolved next hop.). The better discriminating check for this case is: Compare the best route, recursive next-hop resolution, forwarding entry and actual egress interface for the same destination prefix.

This option proposes: Trace source or destination address translation separately from security policy when applications fail across a routed perimeter. It addresses the different topic Huawei firewall NAT and address translation context, not the directly tested Network forwarding planes RIB versus FIB failure in the stated incident (During a maintenance cutover an operator sees a static route in configuration but a line-card forwarding inspection shows an unresolved next hop.).

This option proposes: Trace PIM-SM receiver joins toward an RP and subsequent shortest-path behavior when investigating delayed or suboptimal multicast. It addresses the different topic PIM sparse mode RP shared tree and shortest path transition, not the directly tested Network forwarding planes RIB versus FIB failure in the stated incident (During a maintenance cutover an operator sees a static route in configuration but a line-card forwarding inspection shows an unresolved next hop.).

This option proposes: Diagnose a packet-forwarding discrepancy by separating control-plane routes recorded in the RIB from hardware or software forwarding entries installed in the FIB. It addresses the different topic Network forwarding planes RIB versus FIB, not the directly tested Longest prefix match and route preferences failure in the stated incident (A router has a static default and a learned 10.22.24.0/24 route; a help desk claims every 10.22.24.8 packet must take the static default.).

This option proposes: Design mutual route redistribution to prevent reimporting the same routes and changing their metrics repeatedly. It addresses the different topic Route redistribution feedback loops and route tags, not the directly tested Longest prefix match and route preferences failure in the stated incident (A router has a static default and a learned 10.22.24.0/24 route; a help desk claims every 10.22.24.8 packet must take the static default.).

This option proposes: Use standard BGP communities and import/export policy to label route groups and apply intended traffic-engineering behavior. It addresses the different topic BGP community tagging and route-policy control, not the directly tested Longest prefix match and route preferences failure in the stated incident (A router has a static default and a learned 10.22.24.0/24 route; a help desk claims every 10.22.24.8 packet must take the static default.).

This option proposes: BGP best-path selection evaluates eligibility and multiple attributes in a defined order; higher-stage policy attributes such as LOCAL_PREF can outweigh AS_PATH length, and later tie-breakers apply only as needed. It addresses the different topic BGP route preference sequence and policy precedence, not the directly tested Longest prefix match and route preferences failure in the stated incident (A router has a static default and a learned 10.22.24.0/24 route; a help desk claims every 10.22.24.8 packet must take the static default.).

This option proposes: An OSPF ASBR originates type 5 external LSAs in eligible areas; E1 metrics account for internal cost toward the ASBR, whereas E2 selection prioritizes external cost except for applicable tie-breakers. It addresses the different topic OSPF external LSAs and E1 versus E2 cost, not the directly tested Longest prefix match and route preferences failure in the stated incident (A router has a static default and a learned 10.22.24.0/24 route; a help desk claims every 10.22.24.8 packet must take the static default.).

This option proposes: Routing protocols and static configuration contribute candidate routes to the routing information base, while the forwarding information base contains resolved next-hop and interface data used to forward packets. It addresses the different topic Network forwarding planes RIB versus FIB, not the directly tested Longest prefix match and route preferences failure in the stated incident (A router has a static default and a learned 10.22.24.0/24 route; a help desk claims every 10.22.24.8 packet must take the static default.).

This option proposes: Inspect receiver reports containing include/exclude sources, the configured SSM group range and (S,G) state on multicast routers. It addresses the different topic IGMPv3 source-specific selection and SSM, not the directly tested Longest prefix match and route preferences failure in the stated incident (A router has a static default and a learned 10.22.24.0/24 route; a help desk claims every 10.22.24.8 packet must take the static default.).

This option proposes: Compare the best route, recursive next-hop resolution, forwarding entry and actual egress interface for the same destination prefix. It addresses the different topic Network forwarding planes RIB versus FIB, not the directly tested Longest prefix match and route preferences failure in the stated incident (A router has a static default and a learned 10.22.24.0/24 route; a help desk claims every 10.22.24.8 packet must take the static default.).

This option proposes: Inspect member and master status, stack-link connectivity, dual-active detection mechanisms and forwarding after an isolated partition test. It addresses the different topic Switch stacking clustering and split-brain risk, not the directly tested Longest prefix match and route preferences failure in the stated incident (A router has a static default and a learned 10.22.24.0/24 route; a help desk claims every 10.22.24.8 packet must take the static default.).

That option concerns Network forwarding planes RIB versus FIB. That follows from the targeted action: Investigate routing decisions by checking longest destination-prefix match before comparing preferences among competing routes for that same prefix.

That option concerns ACL traffic filter placement and rule order. That follows from the targeted action: Investigate routing decisions by checking longest destination-prefix match before comparing preferences among competing routes for that same prefix.

That option concerns IP prefix filtering and exact route-match conditions. That follows from the targeted action: Investigate routing decisions by checking longest destination-prefix match before comparing preferences among competing routes for that same prefix.

This option proposes: Configure VRRP priority tracking with suitable preemption behavior so loss of upstream connectivity changes the preferred gateway. It addresses the different topic VRRP interface tracking and controlled preemption, not the directly tested Longest prefix match and route preferences failure in the stated incident (An operations team adds a 192.0.2.128/25 policy route and expects it to be ignored because an older 192.0.2.0/24 route has a lower preference value.).

This option proposes: Analyze BGP best-path choices in a specified platform and release before deciding that the shortest AS_PATH alone always wins. It addresses the different topic BGP route preference sequence and policy precedence, not the directly tested Longest prefix match and route preferences failure in the stated incident (An operations team adds a 192.0.2.128/25 policy route and expects it to be ignored because an older 192.0.2.0/24 route has a lower preference value.).

This option proposes: Diagnose a packet-forwarding discrepancy by separating control-plane routes recorded in the RIB from hardware or software forwarding entries installed in the FIB. It addresses the different topic Network forwarding planes RIB versus FIB, not the directly tested Longest prefix match and route preferences failure in the stated incident (An operations team adds a 192.0.2.128/25 policy route and expects it to be ignored because an older 192.0.2.0/24 route has a lower preference value.).

This option proposes: Routing protocols and static configuration contribute candidate routes to the routing information base, while the forwarding information base contains resolved next-hop and interface data used to forward packets. It addresses the different topic Network forwarding planes RIB versus FIB, not the directly tested Longest prefix match and route preferences failure in the stated incident (An operations team adds a 192.0.2.128/25 policy route and expects it to be ignored because an older 192.0.2.0/24 route has a lower preference value.).

This option proposes: MSTP can map multiple VLANs to different spanning-tree instances and balance paths, but mismatched region parameters place devices in different regions or create a boundary rather than one shared instance. It addresses the different topic MSTP region and VLAN-to-instance mappings, not the directly tested Longest prefix match and route preferences failure in the stated incident (An operations team adds a 192.0.2.128/25 policy route and expects it to be ignored because an older 192.0.2.0/24 route has a lower preference value.).

This option proposes: IP multicast forwarding commonly uses an RPF check toward the source or rendezvous point to prevent loops, so an otherwise reachable multicast group may fail when packets arrive on an unexpected upstream interface. It addresses the different topic Multicast reverse path forwarding checks, not the directly tested Longest prefix match and route preferences failure in the stated incident (An operations team adds a 192.0.2.128/25 policy route and expects it to be ignored because an older 192.0.2.0/24 route has a lower preference value.).

This option proposes: Compare the best route, recursive next-hop resolution, forwarding entry and actual egress interface for the same destination prefix. It addresses the different topic Network forwarding planes RIB versus FIB, not the directly tested Longest prefix match and route preferences failure in the stated incident (An operations team adds a 192.0.2.128/25 policy route and expects it to be ignored because an older 192.0.2.0/24 route has a lower preference value.).

This option proposes: Inspect receiver reports containing include/exclude sources, the configured SSM group range and (S,G) state on multicast routers. It addresses the different topic IGMPv3 source-specific selection and SSM, not the directly tested Longest prefix match and route preferences failure in the stated incident (An operations team adds a 192.0.2.128/25 policy route and expects it to be ignored because an older 192.0.2.0/24 route has a lower preference value.).

This option proposes: Inspect ingress interface VPN instance, per-instance routes, next-hop resolution and authorized route import or interconnect rules. It addresses the different topic VRF traffic separation and route leaking controls, not the directly tested Longest prefix match and route preferences failure in the stated incident (An operations team adds a 192.0.2.128/25 policy route and expects it to be ignored because an older 192.0.2.0/24 route has a lower preference value.).

That option concerns PIM sparse mode RP shared tree and shortest path transition. That follows from the targeted Recommended action: Investigate routing decisions by checking longest destination-prefix match before comparing preferences among competing routes for that same prefix.

That option concerns Network forwarding planes RIB versus FIB. That follows from the targeted Recommended action: Investigate routing decisions by checking longest destination-prefix match before comparing preferences among competing routes for that same prefix.

That option concerns OSPF summarization at ABR and ASBR. That follows from the targeted Recommended action: Investigate routing decisions by checking longest destination-prefix match before comparing preferences among competing routes for that same prefix.

This option proposes: Choose OSPF summarization at the correct boundary and account for reachability when advertising aggregates. It addresses the different topic OSPF summarization at ABR and ASBR, not the directly tested OSPF adjacency prerequisites and mismatched parameters failure in the stated incident (Two campus routers see one another's hello packets but remain in a non-Full state after an interface was moved into a different OSPF area.).

This option proposes: Verify NSSA area behavior and type 7-to-type 5 translation when redistributing an external prefix inside a non-backbone area. It addresses the different topic NSSA type seven translation and default routing, not the directly tested OSPF adjacency prerequisites and mismatched parameters failure in the stated incident (Two campus routers see one another's hello packets but remain in a non-Full state after an interface was moved into a different OSPF area.).

This option proposes: Check route-policy matching conditions, node permit/deny behavior and application direction before fixing unexpected accepted or rejected routes. It addresses the different topic Route-policy node and filtering direction, not the directly tested OSPF adjacency prerequisites and mismatched parameters failure in the stated incident (Two campus routers see one another's hello packets but remain in a non-Full state after an interface was moved into a different OSPF area.).

This option proposes: Packet selection uses the most-specific matching destination route before comparing candidate protocol preferences for identical prefixes; a broad default route does not displace a more-specific valid route solely by lower preference. It addresses the different topic Longest prefix match and route preferences, not the directly tested OSPF adjacency prerequisites and mismatched parameters failure in the stated incident (Two campus routers see one another's hello packets but remain in a non-Full state after an interface was moved into a different OSPF area.).

This option proposes: Passive OSPF interfaces can stop unwanted neighbor discovery while their connected networks may still be advertised through the OSPF process; authentication protects routing exchanges and requires compatible peer settings. It addresses the different topic OSPF interface security and passive network advertisement, not the directly tested OSPF adjacency prerequisites and mismatched parameters failure in the stated incident (Two campus routers see one another's hello packets but remain in a non-Full state after an interface was moved into a different OSPF area.).

This option proposes: On a broadcast network OSPF uses a DR and BDR to limit adjacency overhead; priority zero excludes a candidate, and higher eligible priority and router ID influence a new election rather than forcing instant replacement of a functioning DR. It addresses the different topic OSPF broadcast DR and BDR election, not the directly tested OSPF adjacency prerequisites and mismatched parameters failure in the stated incident (Two campus routers see one another's hello packets but remain in a non-Full state after an interface was moved into a different OSPF area.).