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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.).

This option proposes: Review neighbor state, interface circuit type, NET/area values, hello packets, MTU checks and matching authentication configuration. It addresses the different topic IS-IS area addresses and adjacency prerequisites, 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: 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 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: 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 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: The external route is installed using the intended cost model and an operator can explain why a changed internal path affects E1 differently from E2. It addresses the different topic OSPF external LSAs and E1 versus E2 cost, 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.).

That option concerns OSPF broadcast DR and BDR election. That follows from the targeted action: Check OSPF area type before attempting to import external routes into an area intended to suppress route detail.

That option concerns Multicast reverse path forwarding checks. That follows from the targeted action: Check OSPF area type before attempting to import external routes into an area intended to suppress route detail.

This option proposes: Force every router to restart its OSPF process after discovering mismatched hello intervals, without first correcting the link configuration. It addresses the different topic OSPF adjacency prerequisites and mismatched parameters, 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: Assume the lowest numerical route preference must always override a longer matching prefix for the same destination regardless of mask length. It addresses the different topic Longest prefix match and route preferences, 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: Declare that every OSPF external route uses only internal link-state cost and cannot carry a distinct ASBR-advertised metric. It addresses the different topic OSPF external LSAs and E1 versus E2 cost, 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: Configure DHCP relay to forward broadcast client discovery toward a reachable server and preserve the correct client-subnet context. It addresses the different topic DHCP relay across a routed user VLAN, not the directly tested Stub and totally stub area restrictions failure in the stated incident (A branch ABR injects a default into a stub area, yet a downstream engineer attempts to configure a redistribution ASBR inside that same stub area.).

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 Stub and totally stub area restrictions failure in the stated incident (A branch ABR injects a default into a stub area, yet a downstream engineer attempts to configure a redistribution ASBR inside that same stub area.).

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 Stub and totally stub area restrictions failure in the stated incident (A branch ABR injects a default into a stub area, yet a downstream engineer attempts to configure a redistribution ASBR inside that same stub area.).

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 Stub and totally stub area restrictions failure in the stated incident (A branch ABR injects a default into a stub area, yet a downstream engineer attempts to configure a redistribution ASBR inside that same stub area.).

This option proposes: IS-IS uses CLNS-based network entities and level-specific hellos; level-1 neighbors normally require compatible area membership, while level-2 adjacencies have different area constraints and still need link and authentication compatibility. It addresses the different topic IS-IS area addresses and adjacency prerequisites, not the directly tested Stub and totally stub area restrictions failure in the stated incident (A branch ABR injects a default into a stub area, yet a downstream engineer attempts to configure a redistribution ASBR inside that same stub area.).

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 Stub and totally stub area restrictions failure in the stated incident (A branch ABR injects a default into a stub area, yet a downstream engineer attempts to configure a redistribution ASBR inside that same stub area.).

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 Stub and totally stub area restrictions failure in the stated incident (A branch ABR injects a default into a stub area, yet a downstream engineer attempts to configure a redistribution ASBR inside that same stub area.).

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 Stub and totally stub area restrictions failure in the stated incident (A branch ABR injects a default into a stub area, yet a downstream engineer attempts to configure a redistribution ASBR inside that same stub area.).

This option proposes: Inspect the summarization boundary, contributing active component prefixes, aggregate advertisement and forwarding toward the actual destinations. 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 (A branch ABR injects a default into a stub area, yet a downstream engineer attempts to configure a redistribution ASBR inside that same stub area.).

That option concerns Campus design versus data center fabric operational boundaries. That follows from the targeted Recommended action: Check OSPF area type before attempting to import external routes into an area intended to suppress route detail.

That option concerns OSPF backbone connectivity and virtual link design. That follows from the targeted Recommended action: Check OSPF area type before attempting to import external routes into an area intended to suppress route detail.

That option concerns OSPF adjacency prerequisites and mismatched parameters. That follows from the targeted Recommended action: Check OSPF area type before attempting to import external routes into an area intended to suppress route detail.

This option proposes: Diagnose outbound path choice across iBGP speakers using locally distributed LOCAL_PREF values. It addresses the different topic BGP LOCAL_PREF within one autonomous system, not the directly tested Stub and totally stub area restrictions failure in the stated incident (A branch ABR injects a default into a stub area, yet a downstream engineer attempts to configure a redistribution ASBR inside that same stub area.). The better discriminating check for this case is: Inspect all routers' area flags, ABR default LSA advertisement, permitted LSA types and whether an ASBR is incorrectly placed in the area. The targeted correction is: Check OSPF area type before attempting to import external routes into an area intended to suppress route detail.

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 Stub and totally stub area restrictions failure in the stated incident (A branch ABR injects a default into a stub area, yet a downstream engineer attempts to configure a redistribution ASBR inside that same stub 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 Stub and totally stub area restrictions failure in the stated incident (A branch ABR injects a default into a stub area, yet a downstream engineer attempts to configure a redistribution ASBR inside that same stub area.).

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 NSSA type seven translation and default routing failure in the stated incident (An acquisition branch runs as an NSSA and redistributes a vendor route, but headquarters never learns it because the translator ABR has no usable advertisement.).

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 NSSA type seven translation and default routing failure in the stated incident (An acquisition branch runs as an NSSA and redistributes a vendor route, but headquarters never learns it because the translator ABR has no usable advertisement.).

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 NSSA type seven translation and default routing failure in the stated incident (An acquisition branch runs as an NSSA and redistributes a vendor route, but headquarters never learns it because the translator ABR has no usable advertisement.).

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 NSSA type seven translation and default routing failure in the stated incident (An acquisition branch runs as an NSSA and redistributes a vendor route, but headquarters never learns it because the translator ABR has no usable advertisement.).

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 NSSA type seven translation and default routing failure in the stated incident (An acquisition branch runs as an NSSA and redistributes a vendor route, but headquarters never learns it because the translator ABR has no usable advertisement.).

This option proposes: IS-IS LSP control flags and route-leaking policy determine appropriate reachability; an overload indication can steer other routers away from using an overloaded node as transit while preserving selected directly attached reachability. It addresses the different topic IS-IS routing leakage and overload bit, not the directly tested NSSA type seven translation and default routing failure in the stated incident (An acquisition branch runs as an NSSA and redistributes a vendor route, but headquarters never learns it because the translator ABR has no usable advertisement.).