Chapter 9: Quiz – OSPFv3 (Answers) CCNPv8 ENARSI

1. Which two OSPFv3 LSA types are used to advertise IPv6 unicast address prefixes and prevent the need for SPF calculations every time an address prefix is added or changed on a router interface? (Choose two.)

  • LSA type 4 – inter-area router
  • LSA type 5 – AS-external
  • LSA type 7 – NSSA
  • LSA type 8 – link-local LSA
  • LSA type 9 – intra-area prefix LSA

Explanation: Two new LSA types are added to OSPFv3, type 8, link-local LSA, and type 9, intra-area prefix LSA. These two LSAs advertise unicast prefixes and prevent the need for OSPF calculations when interface addresses are added or changed.

2. When configuring OSPFv3 summarization, on which router should summarization be configured?

  • ABR
  • ASBR
  • DR or BDR
  • any OSPFv3 router in the domain

Explanation: OSPFv3 route summarization must occur on an ABR.

3. What is the result of a router being configured with OSPFv3 for IPv6 when no explicit RID is configured and there are no active IPv4 interfaces?

  • The RID is set to and does not allow adjacencies to form.
  • The RID is set to the first 32 high order bits of the lowest IPv6 address configured on the router.
  • OSPFv3 running IPv6 does not require a RID and IPv6 router adjacencies will form normally.
  • A RID will be automatically generated once an adjacency with another OSPFv3 router is formed.

Explanation: OSPFv3 routers require a valid RID before adjacencies with other OSPFv3 routers can form. A RID can be configured manually using the router-id command or dynamically based on an active IPv4 address.

4. The LS Type field in OSPFv3 LSAs has been increased from 8 bits to 16 bits. What is a purpose of two of the high-order bits in this extended field?

  • to denote the flooding scope of the LSA
  • to carry the ABR RID
  • to indicate the address family (IPv4 or IPv6)
  • to hold the OSPFv3 area ID

Explanation: The three high-order bits of the new LS Type field allow for the encoding of flood information. The first bit indicates how a router should handle an LSA if it is unrecognized. The second and third bits indicate how the LSA should be flooded.

5. Which global configuration command will start OSPFv3 address families routing on a Cisco router?

  • router ospfv3 1
  • ipv6 router ospf 1
  • address-family ipv6 unicast
  • ospfv3 1 ipv6 area 0

Explanation: The OSPFv3 address families routing process is initialized with the router ospfv3 process-idglobal configuration command. The command ipv6 router ospf process-id is a deprecated command that invokes OSPFv3 for IPv6 only. The address-family ipv6 unicast command optionally enables the IPv6 address family automatically on an interface when OSPFv3 is enabled on that interface. The ospfv3 process-id ipv6 area area-id command is an interface command that enables the protocol and assigns the interface to an area.

6. OSPFv3 has three LSA flooding scope types. In addition to area scope what are the other two flooding scopes? (Choose two.)

  • autonomous system
  • link-local
  • not-so-stubby area
  • intra-area prefix
  • AS-external
  • interarea prefix

Explanation: Not-so-stubby area (NSSA), intra-area prefix, AS-external, and interarea prefix are LSA types, not OSPFv3 LSA flooding scopes.

7. Which two statements are true when OSPFv3 with address families is used on routers connecting both IPv4 and IPv6 networks? (Choose two.)

  • IPv6 is used as the protocol to carry the OSPFv3 messages.
  • All connected routers need to have an IPv6 address on the adjacent interfaces.
  • IPv4 is used as the protocol to carry the OSPFv3 IPv4 network messages.
  • IPv6 addressing is not required on the router that is only advertising OSPFv3 routes for IPv4 networks.
  • The OSPFv3 address families feature does not support both IPv4 and IPv6 on the same router.

Explanation: OSPFv3 runs directly over IPv6, and inter-router communication for both IPv4 and IPv6 address families is handled by IPv6 link-local addressing.

8. OSPFv3 authentication supports IPsec AH authentication using the ospfv3 authentication command. In which two instances can the authentication configuration be applied? (Choose two.)

  • to an interface
  • to an entire area
  • to individual ABRs
  • between routers running OSPFv3 and OSPFv2
  • to DR/BDR elections

Explanation: OSPFv3 IPsec authentication can be applied to a router interface, a virtual link, or an entire area. This authentication requires that every router in the area perform IPsec authentication in order to form neighbor adjacencies. IPsec authentication cannot be established between an OPSFv3 router and an OSPFv2 router.

9. Which LSA type is generated by all OSPFv3 routers to describe the state and cost of interfaces in an area?

  • type 1
  • type 2
  • type 3
  • type 4

Explanation: LSA type 1 router LSAs are sent by all OSPFv3 routers to describe the state and cost of interfaces in an area.

1o. Which command should a network technician issue on a Cisco router to display status information about OSPFv3 IPv6 address family neighbor routers?

  • show ospfv3 ipv6 neighbor
  • show ipv6 neighbor
  • show ipv6 route
  • show ipv6 ospf interface

Explanation: The command show ipv6 neighbor displays neighbor information for OSPFv3 for IPv6, not for address families. The command show ipv6 route displays the IPv6 routing table, and the command show ipv6 ospf interface displays information about IPv6 configured interfaces.

11. What IPv6 address does an OSPFv3 router use as the source address for OSPFv3 packets exchanged with OSPFv3 neighbors?

  • the interface link-local address
  • the interface unique global address
  • the all IPv6 routers multicast
  • the all OSPFv3 routers multicast address

Explanation: All OSPFv3 packets area sent using the link-local address of the sending interface as the source IPv6 address.

12. What is the IPv6 address used by OSPFv3 non-DR/BDR routers to send link-state updates and link-state acknowledgments?

  • FF02::2
  • FF02::5
  • FF02::6
  • FF02::9

Explanation: Non-DR/BDR OSPFv3 routers send link-state updates and link acknowledgments to the all DR routers IPv6 multicast address of FF02::6.

“Do I Know This Already?” Quiz Answers:

1. What protocol number does OSPFv3 use for its inter-router communication?

  • 87
  • 88
  • 89
  • 90

Explanation: The IANA has reserved protocol 89 for OSPF.

2. How many packet types does OSPFv3 use for inter-router communication?

  • Three
  • Four
  • Five
  • Six
  • Seven

Explanation: OSPFv2 and OSPFv3 use five packet types for communication: hello, database description, link-state request, link-state update, and link-state acknowledgement.

3. What do you need to do to enable OSPFv3 on an interface?

  • Place the command network prefix/prefix-length under the OSPF process.
  • Place the command network interface-id under the OSPF process.
  • Place the command ospfv3 process-id ipv6 area area-id under the interface.
  • Nothing. OSPFv3 is enabled on all IPv6 interfaces upon initialization of the OSPF process.

Explanation: The command ospfv3 process-id ipv6 area area-id needs to be placed under the interface.

4. True or false: On a brand-new router installation, OSPFv3 requires only an IPv6 linklocal address to be configured and OSPFv3 to be enabled on that interface to form an OSPFv3 neighborship with another router.

  • True
  • False

Explanation: Without an IPv4 address, the router ID is set to, and the router needs to be statically set to form an adjacency with another OSPFv3 router.

5. True or false: OSPFv3 support for IPv4 networks only requires that an IPv4 address be assigned to the interface and that the OSPFv3 process be initialized for IPv4.

  • True
  • False

Explanation: OSPFv3 requires an IPv6 link-local address in order to establish an adjacency to exchange IPv4 or IPv6 routers.

6. Which OSPFv3 flooding scope correlates to the links between two routers?

  • The link-local scope
  • The neighbor scope
  • The process scope
  • The autonomous system scope

Explanation: The link-local scope is limited to the flooding of LSAs between two routers sharing the same link.

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