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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 summarization at ABR and ASBR failure in the stated incident (A campus ABR has many /24 user VLANs and wants to publish a concise inter-area summary without blackholing missing VLAN ranges.).

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 summarization at ABR and ASBR failure in the stated incident (A campus ABR has many /24 user VLANs and wants to publish a concise inter-area summary without blackholing missing VLAN ranges.).

This option proposes: NAT rules change observed packet addresses under defined conditions, and a permitted security rule alone does not create a suitable translation mapping or solve upstream return routing. It addresses the different topic Huawei firewall NAT and address translation context, not the directly tested OSPF summarization at ABR and ASBR failure in the stated incident (A campus ABR has many /24 user VLANs and wants to publish a concise inter-area summary without blackholing missing VLAN ranges.).

This option proposes: Check DR and BDR addresses, each neighbor's interface priority and router ID, network type and whether an election actually occurred. It addresses the different topic OSPF broadcast DR and BDR election, not the directly tested OSPF summarization at ABR and ASBR failure in the stated incident (A campus ABR has many /24 user VLANs and wants to publish a concise inter-area summary without blackholing missing VLAN ranges.).

This option proposes: Review the advertised NEXT_HOP, recursive IGP reachability, iBGP peer configuration and installed BGP route state. It addresses the different topic BGP NEXT_HOP reachability and next-hop-self, not the directly tested OSPF summarization at ABR and ASBR failure in the stated incident (A campus ABR has many /24 user VLANs and wants to publish a concise inter-area summary without blackholing missing VLAN ranges.). The better discriminating check for this case is: Inspect the summarization boundary, contributing active component prefixes, aggregate advertisement and forwarding toward the actual destinations. The targeted correction is: Choose OSPF summarization at the correct boundary and account for reachability when advertising aggregates.

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 summarization at ABR and ASBR failure in the stated incident (A campus ABR has many /24 user VLANs and wants to publish a concise inter-area summary without blackholing missing VLAN ranges.).

That option concerns Stub and totally stub area restrictions. That follows from the targeted action: Choose OSPF summarization at the correct boundary and account for reachability when advertising aggregates.

That option concerns VRRP master election priority and tie breaks. That follows from the targeted action: Choose OSPF summarization at the correct boundary and account for reachability when advertising aggregates.

That option concerns NSSA type seven translation and default routing. That follows from the targeted action: Choose OSPF summarization at the correct boundary and account for reachability when advertising aggregates.

This option proposes: Diagnose an unexpected OSPF intra-area path by comparing cumulative interface costs through the shortest-path tree. It addresses the different topic OSPF SPF calculation and interface cost changes, not the directly tested OSPF summarization at ABR and ASBR failure in the stated incident (A perimeter ASBR redistributes several external service prefixes and the team tries to apply an inter-area aggregation command to them.).

This option proposes: Check the MED value and the policy context before using BGP advertisements to suggest which entry link another AS should prefer. It addresses the different topic BGP MED interpretation between neighboring autonomous systems, not the directly tested OSPF summarization at ABR and ASBR failure in the stated incident (A perimeter ASBR redistributes several external service prefixes and the team tries to apply an inter-area aggregation command to them.).

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 OSPF summarization at ABR and ASBR failure in the stated incident (A perimeter ASBR redistributes several external service prefixes and the team tries to apply an inter-area aggregation command to them.).

This option proposes: OSPF neighbors on a common link must agree on critical adjacency parameters, including compatible area and authentication; repeated resets will not repair a persistent mismatch. It addresses the different topic OSPF adjacency prerequisites and mismatched parameters, not the directly tested OSPF summarization at ABR and ASBR failure in the stated incident (A perimeter ASBR redistributes several external service prefixes and the team tries to apply an inter-area aggregation command to them.).

This option proposes: BGP speakers must reach configured peer addresses and negotiate acceptable AS identities and other session parameters; the Established state is required before normal UPDATE route exchange. It addresses the different topic BGP transport reachability and session states, not the directly tested OSPF summarization at ABR and ASBR failure in the stated incident (A perimeter ASBR redistributes several external service prefixes and the team tries to apply an inter-area aggregation command to them.).

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 summarization at ABR and ASBR failure in the stated incident (A perimeter ASBR redistributes several external service prefixes and the team tries to apply an inter-area aggregation command to them.).

This option proposes: Review the advertised NEXT_HOP, recursive IGP reachability, iBGP peer configuration and installed BGP route state. It addresses the different topic BGP NEXT_HOP reachability and next-hop-self, not the directly tested OSPF summarization at ABR and ASBR failure in the stated incident (A perimeter ASBR redistributes several external service prefixes and the team tries to apply an inter-area aggregation command to them.). The better discriminating check for this case is: Inspect the summarization boundary, contributing active component prefixes, aggregate advertisement and forwarding toward the actual destinations. The targeted correction is: Choose OSPF summarization at the correct boundary and account for reachability when advertising aggregates.

This option proposes: Inspect OSPF neighbor states and interface detail on both ends, including area IDs, hello/dead intervals, network type and authentication settings. It addresses the different topic OSPF adjacency prerequisites and mismatched parameters, not the directly tested OSPF summarization at ABR and ASBR failure in the stated incident (A perimeter ASBR redistributes several external service prefixes and the team tries to apply an inter-area aggregation command to them.).

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 summarization at ABR and ASBR failure in the stated incident (A perimeter ASBR redistributes several external service prefixes and the team tries to apply an inter-area aggregation command to them.).

That option concerns SNMP manager polling traps and authenticated operation. That follows from the targeted Recommended action: Choose OSPF summarization at the correct boundary and account for reachability when advertising aggregates.

That option concerns OSPF external LSAs and E1 versus E2 cost. That follows from the targeted Recommended action: Choose OSPF summarization at the correct boundary and account for reachability when advertising aggregates.

That option concerns OSPF router network and summary LSA scope. That follows from the targeted Recommended action: Choose OSPF summarization at the correct boundary and account for reachability when advertising aggregates.

This option proposes: Assess fast roaming within and between AP coverage cells using the configured mobility relationship and authentication requirements. It addresses the different topic Wireless roaming mobility and session continuity, not the directly tested OSPF interface security and passive network advertisement failure in the stated incident (An operator makes a server-facing VLAN passive and worries that the subnet must disappear from all OSPF routes even though no adjacency was intended there.).

This option proposes: Diagnose an unexpected OSPF intra-area path by comparing cumulative interface costs through the shortest-path tree. It addresses the different topic OSPF SPF calculation and interface cost changes, not the directly tested OSPF interface security and passive network advertisement failure in the stated incident (An operator makes a server-facing VLAN passive and worries that the subnet must disappear from all OSPF routes even though no adjacency was intended there.).

This option proposes: Compare OSPF interface state, area, authentication, timers and network type before resetting a neighbor relationship. It addresses the different topic OSPF adjacency prerequisites and mismatched parameters, not the directly tested OSPF interface security and passive network advertisement failure in the stated incident (An operator makes a server-facing VLAN passive and worries that the subnet must disappear from all OSPF routes even though no adjacency was intended 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 OSPF interface security and passive network advertisement failure in the stated incident (An operator makes a server-facing VLAN passive and worries that the subnet must disappear from all OSPF routes even though no adjacency was intended there.).

This option proposes: BGP communities carry policy markers that can be matched by participating peers, but the markers alone do not enforce filtering unless suitable route-policy rules recognize and act on them. It addresses the different topic BGP community tagging and route-policy control, not the directly tested OSPF interface security and passive network advertisement failure in the stated incident (An operator makes a server-facing VLAN passive and worries that the subnet must disappear from all OSPF routes even though no adjacency was intended there.).

This option proposes: OSPF's intra-area SPF calculation prefers the lowest valid accumulated link cost, subject to equal-cost rules; a protocol neighbor being Full alone does not establish path preference. It addresses the different topic OSPF SPF calculation and interface cost changes, not the directly tested OSPF interface security and passive network advertisement failure in the stated incident (An operator makes a server-facing VLAN passive and worries that the subnet must disappear from all OSPF routes even though no adjacency was intended there.).

This option proposes: Inspect orchestrator policy distribution, WAN link health metrics, site tunnel status, application SLA thresholds and actual selected forwarding path. It addresses the different topic SDN WAN control and SD-WAN policy forwarding, not the directly tested OSPF interface security and passive network advertisement failure in the stated incident (An operator makes a server-facing VLAN passive and worries that the subnet must disappear from all OSPF routes even though no adjacency was intended there.).

This option proposes: Check DR and BDR addresses, each neighbor's interface priority and router ID, network type and whether an election actually occurred. It addresses the different topic OSPF broadcast DR and BDR election, not the directly tested OSPF interface security and passive network advertisement failure in the stated incident (An operator makes a server-facing VLAN passive and worries that the subnet must disappear from all OSPF routes even though no adjacency was intended there.).

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 interface security and passive network advertisement failure in the stated incident (An operator makes a server-facing VLAN passive and worries that the subnet must disappear from all OSPF routes even though no adjacency was intended there.).

That option concerns OSPF router network and summary LSA scope. That follows from the targeted action: Apply OSPF neighbor authentication and passive-interface policy without accidentally suppressing required route advertisements.

That option concerns Stub and totally stub area restrictions. That follows from the targeted action: Apply OSPF neighbor authentication and passive-interface policy without accidentally suppressing required route advertisements.

That option concerns Stateful firewall sessions versus basic packet ACL filtering. That follows from the targeted action: Apply OSPF neighbor authentication and passive-interface policy without accidentally suppressing required route advertisements.