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This option proposes: Type 1 router and type 2 network LSAs describe area-local topology, whereas ABRs create type 3 summary LSAs for destinations in other areas; a lack of appropriate LSAs affects SPF reachability. It addresses the different topic OSPF router network and summary LSA scope, not the directly tested OSPF external LSAs and E1 versus E2 cost failure in the stated incident (A dual-exit enterprise redistributes the same external prefix at two ASBRs and sees traffic prefer one exit despite different internal path costs.).

This option proposes: In any-source PIM-SM an RP supports initial shared-tree joining and source registration, while routers may switch to source-rooted shortest-path trees according to configured behavior and traffic. It addresses the different topic PIM sparse mode RP shared tree and shortest path transition, not the directly tested OSPF external LSAs and E1 versus E2 cost failure in the stated incident (A dual-exit enterprise redistributes the same external prefix at two ASBRs and sees traffic prefer one exit despite different internal path costs.).

This option proposes: Inter-area OSPF design relies on a connected backbone area; virtual links can logically connect certain disconnected backbone segments through a suitable transit area but cannot pass through a stub area. It addresses the different topic OSPF backbone connectivity and virtual link design, not the directly tested OSPF external LSAs and E1 versus E2 cost failure in the stated incident (A dual-exit enterprise redistributes the same external prefix at two ASBRs and sees traffic prefer one exit despite different internal path costs.).

This option proposes: Review manager IP, user security level, permissions, device trap destination, authentication logs and sample interface counters or link-down notifications. It addresses the different topic SNMP manager polling traps and authenticated operation, not the directly tested OSPF external LSAs and E1 versus E2 cost failure in the stated incident (A dual-exit enterprise redistributes the same external prefix at two ASBRs and sees traffic prefer one exit despite different internal path costs.).

This option proposes: Inspect all routers' area flags, ABR default LSA advertisement, permitted LSA types and whether an ASBR is incorrectly placed in the area. It addresses the different topic Stub and totally stub area restrictions, not the directly tested OSPF external LSAs and E1 versus E2 cost failure in the stated incident (A dual-exit enterprise redistributes the same external prefix at two ASBRs and sees traffic prefer one exit despite different internal path costs.).

This option proposes: Compare each candidate path's per-interface costs, SPF route metrics, topology database and resulting next-hop entries. It addresses the different topic OSPF SPF calculation and interface cost changes, not the directly tested OSPF external LSAs and E1 versus E2 cost failure in the stated incident (A dual-exit enterprise redistributes the same external prefix at two ASBRs and sees traffic prefer one exit despite different internal path costs.).

That option concerns OSPF router network and summary LSA scope. That follows from the targeted action: Distinguish redistributed external routes and external cost types when diagnosing a route that enters through an ASBR.

That option concerns OSPF summarization at ABR and ASBR. That follows from the targeted action: Distinguish redistributed external routes and external cost types when diagnosing a route that enters through an ASBR.

That option concerns MSTP region and VLAN-to-instance mappings. That follows from the targeted action: Distinguish redistributed external routes and external cost types when diagnosing a route that enters through an ASBR.

This option proposes: Investigate routing decisions by checking longest destination-prefix match before comparing preferences among competing routes for that same prefix. It addresses the different topic Longest prefix match and route preferences, not the directly tested OSPF external LSAs and E1 versus E2 cost failure in the stated incident (A dual-exit enterprise redistributes the same external prefix at two ASBRs and sees traffic prefer one exit despite different internal path costs.).

This option proposes: Distinguish level-1 area routing from level-2 backbone-style interarea routing when troubleshooting a missing destination. It addresses the different topic IS-IS level one versus level two reachability, not the directly tested OSPF external LSAs and E1 versus E2 cost failure in the stated incident (A dual-exit enterprise redistributes the same external prefix at two ASBRs and sees traffic prefer one exit despite different internal path costs.).

This option proposes: Inspect all routers' area flags, ABR default LSA advertisement, permitted LSA types and whether an ASBR is incorrectly placed in the area. It addresses the different topic Stub and totally stub area restrictions, not the directly tested OSPF external LSAs and E1 versus E2 cost failure in the stated incident (A dual-exit enterprise redistributes the same external prefix at two ASBRs and sees traffic prefer one exit despite different internal path costs.). The better discriminating check for this case is: Inspect the originating ASBR, type 5 LSA, external metric type and metric, cost toward the ASBR and actual selected external next hop.

This option proposes: Check OSPF area type before attempting to import external routes into an area intended to suppress route detail. It addresses the different topic Stub and totally stub area restrictions, not the directly tested OSPF external LSAs and E1 versus E2 cost failure in the stated incident (An engineer changes an ASBR-advertised external route from E2 to E1 and needs to explain how upstream link costs influence next-hop choice.).

This option proposes: Apply OSPF neighbor authentication and passive-interface policy without accidentally suppressing required route advertisements. It addresses the different topic OSPF interface security and passive network advertisement, not the directly tested OSPF external LSAs and E1 versus E2 cost failure in the stated incident (An engineer changes an ASBR-advertised external route from E2 to E1 and needs to explain how upstream link costs influence next-hop choice.).

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 OSPF external LSAs and E1 versus E2 cost failure in the stated incident (An engineer changes an ASBR-advertised external route from E2 to E1 and needs to explain how upstream link costs influence next-hop choice.).

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 external LSAs and E1 versus E2 cost failure in the stated incident (An engineer changes an ASBR-advertised external route from E2 to E1 and needs to explain how upstream link costs influence next-hop choice.).

This option proposes: An NSSA permits its local ASBR to originate type 7 external LSAs that can be translated to type 5 by an eligible ABR, while incoming external type 5 advertisements are not flooded into the NSSA. It addresses the different topic NSSA type seven translation and default routing, not the directly tested OSPF external LSAs and E1 versus E2 cost failure in the stated incident (An engineer changes an ASBR-advertised external route from E2 to E1 and needs to explain how upstream link costs influence next-hop choice.).

This option proposes: IKE negotiates security associations and authenticates peers, while IPsec ESP carries encrypted or integrity-protected traffic as configured; matching peer identities, proposals and traffic selectors are needed for an effective tunnel. It addresses the different topic IPsec VPN IKE negotiation versus ESP data channel, not the directly tested OSPF external LSAs and E1 versus E2 cost failure in the stated incident (An engineer changes an ASBR-advertised external route from E2 to E1 and needs to explain how upstream link costs influence next-hop choice.).

This option proposes: Inspect classifier match counters, behavior actions, traffic-policy associations, interface attachment and ingress/egress direction. It addresses the different topic Huawei MQC traffic classification and behavior binding, not the directly tested OSPF external LSAs and E1 versus E2 cost failure in the stated incident (An engineer changes an ASBR-advertised external route from E2 to E1 and needs to explain how upstream link costs influence next-hop choice.).

This option proposes: Compare the area link-state database, LSA type, advertising router, ABR reachability and route installation for the absent prefix. It addresses the different topic OSPF router network and summary LSA scope, not the directly tested OSPF external LSAs and E1 versus E2 cost failure in the stated incident (An engineer changes an ASBR-advertised external route from E2 to E1 and needs to explain how upstream link costs influence next-hop choice.).

This option proposes: Check whether the interface should form neighbors, its authentication mode, passive state, advertised prefix and neighboring device visibility. It addresses the different topic OSPF interface security and passive network advertisement, not the directly tested OSPF external LSAs and E1 versus E2 cost failure in the stated incident (An engineer changes an ASBR-advertised external route from E2 to E1 and needs to explain how upstream link costs influence next-hop choice.).

That option concerns IPv6 SLAAC RA prefix and duplicate address detection. That follows from the targeted Recommended action: Distinguish redistributed external routes and external cost types when diagnosing a route that enters through an ASBR.

That option concerns OSPF backbone connectivity and virtual link design. That follows from the targeted Recommended action: Distinguish redistributed external routes and external cost types when diagnosing a route that enters through an ASBR.

That option concerns OSPF interface security and passive network advertisement. That follows from the targeted Recommended action: Distinguish redistributed external routes and external cost types when diagnosing a route that enters through an ASBR.

This option proposes: Map the ABRs, area membership, transit-area properties and database synchronization along the proposed virtual-link path. It addresses the different topic OSPF backbone connectivity and virtual link design, not the directly tested OSPF external LSAs and E1 versus E2 cost failure in the stated incident (An engineer changes an ASBR-advertised external route from E2 to E1 and needs to explain how upstream link costs influence next-hop choice.).

This option proposes: Trace an enterprise wireless AP's registration to its access controller and the separation of management from user traffic in supported forwarding modes. It addresses the different topic Large campus WLAN AC AP and CAPWAP architecture, not the directly tested OSPF external LSAs and E1 versus E2 cost failure in the stated incident (An engineer changes an ASBR-advertised external route from E2 to E1 and needs to explain how upstream link costs influence next-hop choice.).

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 OSPF external LSAs and E1 versus E2 cost failure in the stated incident (An engineer changes an ASBR-advertised external route from E2 to E1 and needs to explain how upstream link costs influence next-hop choice.).

This option proposes: Identify OSPF LSA types and their flooding scope before diagnosing missing intra-area or inter-area destinations. It addresses the different topic OSPF router network and summary LSA scope, not the directly tested Stub and totally stub area restrictions failure in the stated incident (An office area is converted to totally stub but a remote administrator still expects individual type 3 inter-area prefixes to appear there.).

This option proposes: Verify the match criteria and behavior binding in a Modular QoS Command-Line configuration before investigating packet-marking or policing failures. It addresses the different topic Huawei MQC traffic classification and behavior binding, not the directly tested Stub and totally stub area restrictions failure in the stated incident (An office area is converted to totally stub but a remote administrator still expects individual type 3 inter-area prefixes to appear there.).

This option proposes: Evaluate non-backbone OSPF connectivity through area 0 and whether a virtual link is an appropriate temporary correction in supported topologies. It addresses the different topic OSPF backbone connectivity and virtual link design, not the directly tested Stub and totally stub area restrictions failure in the stated incident (An office area is converted to totally stub but a remote administrator still expects individual type 3 inter-area prefixes to appear there.).

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 Stub and totally stub area restrictions failure in the stated incident (An office area is converted to totally stub but a remote administrator still expects individual type 3 inter-area prefixes to appear there.).

This option proposes: An ABR can summarize inter-area routes and an ASBR can summarize redistributed external routes; aggregation reduces route detail but can hide component failures or create blackholes without safeguards. It addresses the different topic OSPF summarization at ABR and ASBR, not the directly tested Stub and totally stub area restrictions failure in the stated incident (An office area is converted to totally stub but a remote administrator still expects individual type 3 inter-area prefixes to appear there.).

This option proposes: A stateful firewall tracks valid connection context and can permit related return traffic based on session state; network ACLs may filter packets independently without the same stateful application tracking. It addresses the different topic Stateful firewall sessions versus basic packet ACL filtering, not the directly tested Stub and totally stub area restrictions failure in the stated incident (An office area is converted to totally stub but a remote administrator still expects individual type 3 inter-area prefixes to appear there.).