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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 SPF calculation and interface cost changes failure in the stated incident (A campus core prefers a three-link path over a direct uplink because the direct link's OSPF cost was raised for maintenance.).

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 SPF calculation and interface cost changes failure in the stated incident (A campus core prefers a three-link path over a direct uplink because the direct link's OSPF cost was raised for maintenance.).

This option proposes: MED is an optional nontransitive BGP attribute, with lower values typically favored when compared under applicable rules; it is often compared for routes from the same neighboring AS unless policy changes this behavior. It addresses the different topic BGP MED interpretation between neighboring autonomous systems, not the directly tested OSPF SPF calculation and interface cost changes failure in the stated incident (A campus core prefers a three-link path over a direct uplink because the direct link's OSPF cost was raised for maintenance.).

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 SPF calculation and interface cost changes failure in the stated incident (A campus core prefers a three-link path over a direct uplink because the direct link's OSPF cost was raised for maintenance.).

This option proposes: Compare candidate route validity, policy preferences, AS_PATH lengths, origins, MED, eBGP/iBGP learning mode and relevant platform-specific tie-break rules. It addresses the different topic BGP route preference sequence and policy precedence, not the directly tested OSPF SPF calculation and interface cost changes failure in the stated incident (A campus core prefers a three-link path over a direct uplink because the direct link's OSPF cost was raised for maintenance.).

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 SPF calculation and interface cost changes failure in the stated incident (A campus core prefers a three-link path over a direct uplink because the direct link's OSPF cost was raised for maintenance.).

That option concerns OSPF summarization at ABR and ASBR. That follows from the targeted action: Diagnose an unexpected OSPF intra-area path by comparing cumulative interface costs through the shortest-path tree.

That option concerns OSPF router network and summary LSA scope. That follows from the targeted action: Diagnose an unexpected OSPF intra-area path by comparing cumulative interface costs through the shortest-path tree.

That option concerns Longest prefix match and route preferences. That follows from the targeted action: Diagnose an unexpected OSPF intra-area path by comparing cumulative interface costs through the shortest-path tree.

This option proposes: Expect an EVPN Type 2 MAC advertisement alone to make an unreachable underlay VTEP routable without any transport path. It addresses the different topic MP-BGP EVPN route types and forwarding separation, not the directly tested OSPF SPF calculation and interface cost changes failure in the stated incident (A campus core prefers a three-link path over a direct uplink because the direct link's OSPF cost was raised for maintenance.).

This option proposes: Expect a newly connected router with priority 255 to immediately seize the DR role from a healthy established designated router with no new election. It addresses the different topic OSPF broadcast DR and BDR election, not the directly tested OSPF SPF calculation and interface cost changes failure in the stated incident (A campus core prefers a three-link path over a direct uplink because the direct link's OSPF cost was raised for maintenance.).

This option proposes: Build an OSPF virtual link through a stub transit area and assume the special-area flag has no influence on its eligibility. It addresses the different topic OSPF backbone connectivity and virtual link design, not the directly tested OSPF SPF calculation and interface cost changes failure in the stated incident (A campus core prefers a three-link path over a direct uplink because the direct link's OSPF cost was raised for maintenance.).

This option proposes: Review broadcast-network designated-router election based on interface priority and router ID, noting that a stable election does not automatically preempt. It addresses the different topic OSPF broadcast DR and BDR election, not the directly tested OSPF SPF calculation and interface cost changes failure in the stated incident (After a bandwidth upgrade a routing administrator changes OSPF interface costs and needs to predict whether a previously secondary path becomes best.).

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 SPF calculation and interface cost changes failure in the stated incident (After a bandwidth upgrade a routing administrator changes OSPF interface costs and needs to predict whether a previously secondary path becomes best.).

This option proposes: Check IGMP membership and querier operation on the receiver LAN before changing PIM routing configuration upstream. It addresses the different topic IGMP querier membership reports and group timeout, not the directly tested OSPF SPF calculation and interface cost changes failure in the stated incident (After a bandwidth upgrade a routing administrator changes OSPF interface costs and needs to predict whether a previously secondary path becomes best.).

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 SPF calculation and interface cost changes failure in the stated incident (After a bandwidth upgrade a routing administrator changes OSPF interface costs and needs to predict whether a previously secondary path becomes best.).

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 OSPF SPF calculation and interface cost changes failure in the stated incident (After a bandwidth upgrade a routing administrator changes OSPF interface costs and needs to predict whether a previously secondary path becomes best.).

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 OSPF SPF calculation and interface cost changes failure in the stated incident (After a bandwidth upgrade a routing administrator changes OSPF interface costs and needs to predict whether a previously secondary path becomes best.).

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 SPF calculation and interface cost changes failure in the stated incident (After a bandwidth upgrade a routing administrator changes OSPF interface costs and needs to predict whether a previously secondary path becomes best.).

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 SPF calculation and interface cost changes failure in the stated incident (After a bandwidth upgrade a routing administrator changes OSPF interface costs and needs to predict whether a previously secondary path becomes best.).

This option proposes: Inspect the originating ASBR, type 5 LSA, external metric type and metric, cost toward the ASBR and actual selected external next hop. It addresses the different topic OSPF external LSAs and E1 versus E2 cost, not the directly tested OSPF SPF calculation and interface cost changes failure in the stated incident (After a bandwidth upgrade a routing administrator changes OSPF interface costs and needs to predict whether a previously secondary path becomes best.).

That option concerns MSTP region and VLAN-to-instance mappings. That follows from the targeted Recommended action: Diagnose an unexpected OSPF intra-area path by comparing cumulative interface costs through the shortest-path tree.

That option concerns Stub and totally stub area restrictions. That follows from the targeted Recommended action: Diagnose an unexpected OSPF intra-area path by comparing cumulative interface costs through the shortest-path tree.

That option concerns OSPF adjacency prerequisites and mismatched parameters. That follows from the targeted Recommended action: Diagnose an unexpected OSPF intra-area path by comparing cumulative interface costs through the shortest-path tree.

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 OSPF SPF calculation and interface cost changes failure in the stated incident (After a bandwidth upgrade a routing administrator changes OSPF interface costs and needs to predict whether a previously secondary path becomes best.).

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 SPF calculation and interface cost changes failure in the stated incident (After a bandwidth upgrade a routing administrator changes OSPF interface costs and needs to predict whether a previously secondary path becomes best.).

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 SPF calculation and interface cost changes failure in the stated incident (After a bandwidth upgrade a routing administrator changes OSPF interface costs and needs to predict whether a previously secondary path becomes best.).

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 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: Distinguish redistributed external routes and external cost types when diagnosing a route that enters through an ASBR. It addresses the different topic OSPF external LSAs and E1 versus E2 cost, 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: Validate physical stack links, member roles and split-brain safeguards before considering a multi-switch logical chassis redundant. It addresses the different topic Switch stacking clustering and split-brain risk, 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: 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.).