CCDA FAQ: OSPF, BGP, Route Manipulation, and IP Multicast

Q1. True or false: A router needs to have all its interfaces in Area 0 to be considered an OSPF backbone router.

Answer: False. A router with one or more interfaces in Area 0 is considered an OSPF backbone router.

Q2. True or false: OSPF IS-IS uses a designated router in multiaccess networks.

Answer: True

Q3. Which multicast addresses do OSPFv2 routers use?

Answer: 224.0.0.5 for ALLSPFRouters and 224.0.0.6 for ALLDRouters.

Q4. Which multicast addresses are used by OSPFv3 routers?

Answer: FF02::5 for ALLSPFRouters and FF02::6 for ALLDRouters.

Q5. What is the Cisco administrative distance of OSPF?

Answer: The administrative distance of OSPF is 110.

Q6. Which OSPFv2 router type generates the OSPF Type 3 LSA?

Answer: OSPF ABRs generate the Type 3 summary LSA for ABRs.

Q7. Which OSPFv2 router type generates the OSPF Type 2 LSA?

Answer: OSPF DRs generate Type 2 network LSAs.

Q8. What is included in an OSPFv2 router LSA?

Answer: Included are the router’s links, interfaces, state of links, and cost.

Q9. True or false: The router with the lowest priority is selected as the OSPF DR.

Answer: False. The router with the highest priority is selected as the OSPF designated router.

Q10. True or false: You use iBGP to exchange routes between different autonomous systems.

Answer: False. You use eBGP to exchange routes between different autonomous systems.

Q11. True or false: BGP Version 4 does not include support for CIDR, only OSPF and EIGRP do.

Answer: False. BGPv4 added support for classless interdomain routing (CIDR), which provides the capability of forwarding packets based on IP prefixes only, with no concern for the address class.

Q12. True or false: eBGP and iBGP redistribute automatically on a router if the BGP peers are configured with the same autonomous system number.

Answer: True

Q13. eBGP routes have an administrative distance of ____, and iBGP routes have an administrative distance of ____.

Answer: 20, 200

Q14. True or false: IGMP snooping and CGMP are methods to reduce the multicast traffic at Layer 2.

Answer: True

Q15. True or false: PIM has a hop-count limit of 32.

Answer: False. PIM does not have a hop-count limit. DVMRP has a hop-count limit of 32.

Q16. True or false: PIM-SM routers use the multicast 224.0.0.13 address to request a multicast group to the RP.

Answer: True

Q17. True or false: autonomous system path is the only attribute BGP uses to determine the best path to the destination.

Answer: False. BGP uses several attributes in the BGP decision process.

Q18. List three IP routing protocols that use multicast addresses to communicate with their neighbors.

Answer: RIPv2, OSPF, and EIGRP.

Q19. What IPv6 multicast address does EIGRP use for IPv6?

Answer: FF02::A

Q20. Match the routing protocol with the description:
i. EIGRP
ii. OSPFv2
iii. RIPv2
iv. BGP
a. Distance-vector protocol used in the edge of the network
b. IETF link-state protocol used in the network core
c. Hybrid protocol used in the network core
d. Path-vector protocol

Answer: i = C, ii = B, iii = A, iv = D

Q21. What is the default OSPF cost for a Fast Ethernet interface?

Answer: Cost is calculated as 108 / BW, and BW = 100 Mbps = 108 bps for Fast Ethernet. Cost = 108 / 108 = 1.

Q22. Which routing protocol do you use in the core of a large enterprise network that supports VLSMs for a network with a mix of Cisco and non-Cisco routers?

Answer: OSPF. Although RIPv2 and EIGRP support VLSMs, RIPv2 is no longer recommended. EIGRP is not supported on non-Cisco routers.

Q23. What is the benefit of designing for stub areas?

Answer: You do not need to flood external LSAs into the stub area, which reduces LSA traffic.

Q24. What constraint does the OSPF network design have for traffic traveling between areas?

Answer: All traffic from one area must travel through Area 0 (the backbone) to get to another area.

Q25. How is OSPFv3 identified as the upper-layer protocol in IPv6?

Answer: OSPFv3 is identified as IPv6 Next Header 89.

Q26. Which routing protocols are recommended for large enterprise networks?
a. RIPv2
b. OSPFv2
c. EIGRP
d. IS-IS
e. A and B
f. B and C
g. B and D
h. A, B, C, and D

Answer: F. EIGRP and OSPFv2 are recommended for large enterprise networks.

Q27. What OSPFv3 has an LS type of 0x0008?
a. Router LSA
b. Interarea-router LSA
c. Link LSA
d. Intra-area-prefix LSA

Answer: C. Link LSAs are flooded to the local link.

Q28. Which routing protocol does not support VLSMs?
a. RIPv1
b. OSPFv2
c. EIGRP
d. RIPv2
e. B and C
f. B, C, and D

Answer: F. RIPv1 does not support VLSMs.

Q29. Which routing protocols have fast convergence for IPv4 networks?
a. BGP
b. OSPFv2
c. EIGRP
d. RIPv2
e. B and C
f. B, C, and D
g. A, B, and C

Answer: E. EIGRP and OSPFv2 have fast convergence.

Q30. Which routing protocols have fast convergence for IPv6 networks?
a. RIPng
b. OSPFv3
c. EIGRP for IPv6
d. RIPv2
e. MP-BGP
f. B and C
g. B, C, and D
h. B, C, and E

Answer: F. EIGRP for IPv6 and OSPFv3 have fast convergence for IPv6 networks.

Q31. A retail chain has about 800 stores that connect to the headquarters and a backup location. The company wants to limit the amount of routing traffic used on the WAN links. What routing protocol(s) is/are recommended?
a. RIPv1
b. RIPv2
c. OSPFv2
d. EIGRP
e. IS-IS
f. BGP
g. B, C, and D
h. C and D
i. C, D, and E

Answer: H. RIPv1 and RIPv2 generate periodic routing traffic. IS-IS is used in SP networks. BGP is used for external networks.

Q32. Which of the following statements is correct?
a. OSPFv3 provides changes to OSPFv2 for use in IPv4 networks.
b. OSPFv3 provides changes to OSPFv2 for use in IPv6 networks.
c. OSPFv3 provides changes to OSPFv2 for use in IPv6 and IPv4 networks.
d. OSPFng provides changes to OSPFv2 for use in IPv6 networks.

Answer: B. OSPFv3 is used in IPv6 networks.

Use Figure to answer the following question.

Figure: Path Selection

Q33. If OSPF is enabled on all routers with the default metrics unchanged, what path is taken?
a. Path 1
b. Path 2
c. Unequal load balance with Path 1 and Path 2
d. Equal load balance with Path 1 and Path 2

Answer: B. From Router A, the OSPF cost for Path 1 is 108 / 256 kbps = 390. The OSPF cost for Path 2 is (108 / 1536 kbps) + (108 / 1024 kbps) + (108 / 768 kbps) = 65 + 97 + 130 = 292. OSPF selects Path 2 because it has a lower cost.

Use Figure to answer the following question. ccda-faq-ospf-bgp-route-manipulation-and-ip-multicast-2
Figure: OSPF Router Types

Q34. Identify the OSPF router types shown in Figure.
Router A = _______
Router B = _______
Router C = _______
Router D = _______
Router E = _______
Router F = _______

Answer: Router A = Internal; Router B = ABR; Router C = Backbone; Router D = ASBR; Router E = ABR; Router F = Internal.

Q35. Match the IP multicast address with its description.
i. 224.0.0.1
ii. 224.0.0.2
iii. 224.0.0.5
iv. 224.0.0.10
a. All OSPF routers
b. All routers
c. EIGRP routers
d. All hosts

Answer: i =D, ii = B, iii = A, iv = C

Q36. Match the BGP attribute with its description.
i. Local preference
ii. MED
iii. Autonomous system path
iv. Next hop
a. IP address
b. Indicates the path used to exit the autonomous system
c. Tells external BGP peers the preferred path into the autonomous system
d. List of ASNs

Answer: i = B, ii = C, iii = D, iv = A

Q37. Which Cisco feature can you use instead of local preference to influence the selected path to external BGP routers?

Answer: Weight. Weight is configured locally and not exchanged in BGP updates. On the other hand, the local preference attribute is exchanged between iBGP peers and is configured at the gateway router.

Q38. What is the purpose of route reflectors?

Answer: Route reflectors reduce the number of iBGP logical mesh connections.

Q39. When BGP confederations are used, which number do external peers see?

Answer: External peers see the confederation ID. The internal private autonomous system numbers are used within the confederation.

Q40. With ____________ all routers peer with each other within the private autonomous system, and with __________ client routers peer only with the reflector.

Answer: BGP confederations, route reflectors.

Q41. Which of the following shows the correct order that BGP uses to select a best path?
a. Origin, lowest IP, autonomous system path, weight, local preference, MED
b. Weight, local preference, autonomous system path, origin, MED, lowest IP
c. Lowest IP, autonomous system path, origin, weight, MED, local preference
d. Weight, origin, local preference, autonomous system path, MED, lowest IP

Answer: B. Only answer B has the correct order of BGP path selection, which is weight, local preference, autonomous system path, origin, MED, and lowest IP.

Q42. What feature did BGPv4 implement to provide forwarding of packets based on IP prefixes?

Answer: CIDR was first implemented in BGPv4.

Q43. What route should be used to summarize the following networks?
10.150.80.0/23, 10.150.82.0/24, 10.150.83.0/24, 10.150.84.0/22
a. 10.150.80.0/23, 10.150.82.0/23, and 10.150.84.0/22
b. 10.150.80.0/22 and 10.150.84/22
c. 10.150.80.0/21
d. 10.150.80.0/20

Answer: C

Q44. Match the IPv6 multicast address with its description.
i. FF02::1
ii. FF02::2
iii. FF02::5
iv. FF02::9
v. FF02::A
a. OSPFv3 routers
b. RIPng routers
c. All routers
d. EIGRP routers
e. All nodes

Answer: i = E, ii = C, iii = A, iv = B, v = D

Q45. Route summarization and redistribution occur in which layer of the hierarchical model?
a. Building access
b. Distribution
c. Core
d. Server access

Answer: B

Q46. Which of the following best describes route summarization?
a. Grouping contiguous addresses to advertise a large Class A network
b. Grouping noncontiguous addresses to advertise a larger network
c. Grouping contiguous addresses to advertise a larger network
d. Grouping Internet addresses

Answer: C

Refer to Figure to answer the following questions 47-50.
ccda-faq-ospf-bgp-route-manipulation-and-ip-multicast-3
Figure: Network Scenario

Q47. Where should you configure BGP?
a. Routers A and B
b. Routers C and D
c. Answers A and B
d. Routers A and C

Answer: B. BGP should be configured between autonomous system 100 and autonomous system 500.

Q48. On which router should you configure redistribution for OSPF and EIGRP?
a. Router A only
b. Router B only
c. Routers A and B
d. Redistribution occurs automatically.

Answer: C. Both Routers A and B perform the redistribution with route filters to prevent route feedback.

Q49. To announce the networks from autonomous system 100 to autonomous system 500, which routing protocols should you redistribute into BGP?
a. OSPF only
b. EIGRP only
c. OSPF and EIGRP
d. iBGP

Answer: B. The OSPF routes are redistributed into EIGRP. Then you can redistribute EIGRP routes into BGP.

Q50. Where should you use filters?
a. Routers A and B
b. Routers C and D
c. Routers A and C
d. Answers A and B

Answer: D. You should use filters on all routers performing redistribution.

Q51. Which protocol defines an Area Border Router (ABR)?
a. Enhanced Interior Gateway Routing Protocol (EIGRP)
b. Open Shortest Path First (OSPF)
c. Intermediate System-to- Intermediate System (IS-IS)
d. Routing Information Protocol (RIP)

Answer: B. OSPF defines ABRs that connect areas to the OSPF backbone.

Q52. Which routing protocols support variable-length subnet masks (VLSM)?
a. EIGRP
b. OSPF
c. IS-IS
d. A and B
e. A and C
f. B and C
g. A, B, and C

Answer: G. EIGRP, OSPF, and IS-IS support VLSMs.

Q53. What is an ASBR?
a. Area Border Router
b. Autonomous System Boundary Router
c. Auxiliary System Border Router
d. Area System Border Router

Answer: B. OSPF defines the ASBR as the router that injects external routes into the OSPF autonomous system.

Q54. What is the OSPFv2 link-state advertisement (LSA) type for autonomous system external LSAs?
a. Type 1
b. Type 2
c. Type 3
d. Type 4
e. Type 5

Answer: E. OSPFv2 Type 5 LSAs are autonomous system external LSAs.

Q55. What address do you use to multicast to the OSPFv2 designated router (DR)?
a. 224.0.0.1
b. 224.0.0.5
c. 224.0.0.6
d. 224.0.0.10

Answer: C. OSPFv2 routers use 224.0.0.6 to communicate with DRs.

Q56. To where are OSPF Type 1 LSAs flooded?
a. The OSPF area
b. The OSPF domain
c. From the area to the OSPF backbone
d. Through the virtual link

Answer: A. Type 1 LSAs (router LSAs) are forwarded to all routers within an OSPF area.

Q57. What OSPFv3 LSA carries address prefixes?
a. Network LSA
b. Summary LSA
c. Interarea-router LSA
d. Intra-area-prefix LSA

Answer: D. Intra-area-prefix LSAs carry IPv6 prefixes associated with a router, a stub network, or an associated transit network segment.

Q58. What protocol do you use to exchange IP routes between autonomous systems?
a. IGMP
b. eBGP
c. EIGRP
d. OSPF

Answer: B. You use External Border Gateway Protocol (eBGP) to exchange routes between autonomous systems.

Q59. Where should routes be summarized?
a. On the core routers
b. On the distribution routers
c. On the access routers
d. None of the above

Answer: B. It is a best practice to summarize routes on the distribution routers toward the core.

Q60. What is IGMP?
a. Interior Group Management Protocol
b. Internet Group Management Protocol
c. Interior Gateway Routing Protocol
d. Interior Gateway Media Protocol

Answer: B. You use IGMP between hosts and local routers to register with multicast groups.

Q61. How many bits are mapped from the Layer 3 IPv4 multicast address to a Layer 2 MAC address?
a. 16 bits
b. 23 bits
c. 24 bits
d. 32 bits

Answer: B. The lower 23 bits of the IP multicast address are mapped to the last 23 bits of the Layer 2 MAC address.

Q62. What is the administrative distance of eBGP routes?
a. 20
b. 100
c. 110
d. 200

Answer: A. The administrative distance of eBGP routes is 20. The administrative distance of Internal BGP (iBGP) routes is 200.

Q63. What is CIDR?
a. Classful intradomain routing
b. Classful interior domain routing
c. Classless intradomain routing
d. Classless interdomain routing

Answer: D. CIDR provides the capability to forward packets based on IP prefixes only, with no concern for IP address class boundaries.

CCDA FAQ: OSPF, BGP, Route Manipulation, and IP Multicast

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