Advanced OSPF & OSPFv3 Practice Questions

Answers and explanations appear when you work through the set above.

1. An ASBR redistributes EIGRP routes into OSPF Area 5, which is a regular (non-stub) area. Which LSA type carries those external routes to routers inside Area 5?

   • Type 5 AS External LSA
   • Type 3 Summary LSA
   • Type 7 NSSA External LSA
   • Type 2 Network LSA

2. Area 20 is configured as an NSSA and has a local ASBR redistributing static routes. Which LSA type does that ASBR generate inside the NSSA?

   • Type 5 AS External LSA
   • Type 4 ASBR Summary LSA
   • Type 7 NSSA External LSA
   • Type 1 Router LSA

3. Which router is responsible for translating a Type 7 LSA into a Type 5 LSA as it leaves an NSSA?

   • Any internal router in the NSSA
   • The NSSA's ABR
   • The Designated Router of the NSSA
   • The router with the lowest router ID in Area 0

4. A totally stubby area is configured on an ABR. Compared to a plain stub area, what additional LSA type does the ABR withhold from that area?

   • Type 1 Router LSAs
   • Type 2 Network LSAs
   • Type 3 Summary LSAs for inter-area routes (a default route is injected instead)
   • Type 7 LSAs

5. Two OSPF areas, Area 0 and Area 30, no longer share a direct physical link because a transit router was removed, but both areas still exist. Which feature restores logical connectivity to Area 0 without adding new physical cabling?

   • A virtual link configured through a transit area
   • A stub area declaration on Area 30
   • A Type 3 LSA filter
   • An OSPF default-information originate statement

6. Which statement about OSPF virtual links is accurate?

   • A virtual link can be configured through a stub area
   • A virtual link's transit area must not itself be a stub area
   • Virtual links do not require a transit area at all
   • Virtual links can only be configured between two ABRs already in Area 0

7. On a multi-access Ethernet segment, two OSPF routers are stuck in the 2-Way state with each other while a DR and BDR have already been elected on that segment. What is the most likely explanation?

   • Their OSPF process IDs do not match
   • Neither of these two routers is the DR or BDR, so they correctly stay in 2-Way with each other (DROTHERs only reach Full with the DR/BDR)
   • Their hello and dead timers are mismatched
   • One of them has the wrong area ID

8. Two routers on the same Ethernet segment are stuck in the ExStart state and never progress to Exchange. What is the most common root cause?

   • A mismatched OSPF area ID
   • A mismatched interface MTU
   • A mismatched hello interval
   • A missing network statement

9. An OSPF neighbor relationship never leaves the Init state. What does this indicate about hello packet flow between the two routers?

   • Hellos are flowing bidirectionally but LSAs are being filtered
   • This router is receiving hellos from the neighbor, but the neighbor has not yet seen its own router ID reflected back
   • The two routers are in different OSPF areas
   • The DR election has not yet completed

10. Two routers connected by a point-to-point serial link fail to form an OSPF adjacency, and their configured network types are both point-to-point. What is a plausible explanation ruled out by that match?

    • Mismatched hello/dead timers
    • Missing DR/BDR election, since point-to-point links never elect one
    • Mismatched OSPF network type causing timer mismatch
    • Mismatched authentication keys

11. An OSPF network is configured as point-to-multipoint non-broadcast on a hub-and-spoke Frame Relay style topology. Which two properties correctly describe this network type?

    • No DR/BDR is elected, and neighbor statements must be manually configured
    • A DR/BDR is elected, and hellos are broadcast automatically
    • No DR/BDR is elected, and hellos are broadcast automatically
    • A DR/BDR is elected, and neighbor statements must be manually configured

12. Which OSPF network type both elects a DR/BDR and requires manually configured neighbor statements?

    • Broadcast
    • Point-to-Point
    • Non-Broadcast Multi-Access (NBMA)
    • Point-to-Multipoint Broadcast

13. Two OSPF routers on the same segment have identical hello and dead intervals but different OSPF network types (one broadcast, one point-to-point). What is the most likely outcome?

    • They reach FULL, but routes across the link are missing because each router describes the link differently in its Router LSA
    • They fail to form an adjacency because DR/BDR expectations differ between the two network types
    • They form an adjacency but never exchange LSAs
    • They form an adjacency only if both are DROTHERs

14. Which timer mismatch alone is sufficient to prevent two OSPF neighbors from ever forming an adjacency?

    • Mismatched retransmit interval
    • Mismatched hello or dead interval
    • Mismatched transmit delay
    • Mismatched LSA refresh interval

15. On a broadcast segment where two routers report the exact same OSPF router ID, what symptom is most likely to appear?

    • Both routers form a stable full adjacency
    • Neighbor state flaps or one router is silently ignored, since router IDs must be unique within the OSPF domain
    • The segment automatically renumbers one router's ID
    • OSPF falls back to using loopback IP addresses instead

16. Which authentication mismatch would prevent an OSPF adjacency from forming even though hellos are otherwise received correctly?

    • Mismatched OSPF process IDs
    • Mismatched authentication type or key between the two interfaces
    • Mismatched interface bandwidth values used for cost calculation
    • Mismatched loopback interface numbering

17. An OSPFv3 router originates a Link LSA (Type 8) on an Ethernet interface. What information does that LSA primarily advertise?

    • Inter-area IPv6 prefixes learned from other areas
    • The router's link-local IPv6 address and the IPv6 prefixes directly attached to that link
    • External routes redistributed from BGP
    • The area's designated router priority list

18. In OSPFv3, actual IPv6 prefix information for intra-area routes is carried in which LSA type, separate from the Router and Network LSAs?

    • Type 8 Link LSA
    • Type 9 Intra-Area-Prefix LSA
    • Type 3 Inter-Area-Prefix LSA
    • Type 7 NSSA External LSA

19. An OSPFv3 process is enabled on a router that has no IPv4 addresses configured on any interface, only IPv6. What must be manually set for OSPFv3 to function correctly?

    • A dual-stack address family under the OSPFv3 process
    • An explicit router ID, since OSPFv3 still uses a 32-bit router ID and cannot derive one from an IPv4 address
    • A default route pointing to the DR
    • A Type 3 LSA filter on every interface

20. Which multicast address do OSPFv3 routers use to reach the DR and BDR specifically, analogous to 224.0.0.6 in OSPFv2?

    • FF02::5
    • FF02::6
    • FF02::1
    • FF02::A

21. OSPFv3 is enabled for both IPv4 and IPv6 on the same router using address families under a single process. Which statement about this design is accurate?

    • OSPFv3 with address families lets one process instance run both IPv4 and IPv6 topologies while keeping their LSA databases separate
    • OSPFv3 can only ever route IPv6, address families are unrelated to IPv4 support
    • Address-family support merges the IPv4 and IPv6 SPF trees into a single calculation
    • OSPFv3 address families require OSPFv2 to also be running for IPv4 reachability

22. An OSPF stub area is configured, but an administrator also wants ASBRs elsewhere in the domain to inject a specific external route summary rather than relying only on the ABR's default route. What is the correct assessment?

    • This is possible, stub areas can carry selected Type 5 LSAs if filtered
    • This is not possible, stub areas block all Type 5 LSAs unconditionally; only NSSA can locally originate limited external-like routes via Type 7
    • Stub areas automatically summarize all external routes without configuration
    • Stub areas require Type 4 LSAs to reach ASBRs directly

23. A router in Area 7 needs to reach an ASBR located in a different, non-backbone area. Which LSA type tells routers in Area 7 how to reach that remote ASBR?

    • Type 3 Summary LSA
    • Type 4 ASBR Summary LSA
    • Type 1 Router LSA
    • Type 7 NSSA External LSA