2022年Cisco,-,最新题库 .pdf

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1、642-611 MPLS - Implementing Cisco MPLS Exam Number: 642-611 Exam A QUESTION 1 Which IOS command should you use to list routers in an LSRs adjacency table? A. show tag tdp nei B. show tag tdp adj C. show tag tdp sum D. show tag tdp detail Answer: A Section: (none) Explanation/Reference: Explanation:

2、The TDP neighbors and the status of individual TDP sessions also can be monitored with the show tag tdp neighbor command. The command displays the TDP identifiers of the local and remote routers, the IP addresses and the TCP port numbers between the TDP connection is established, the connection upti

3、me and the interfaces through which the TDP neighbor was discovered, as well as all the interface IP addresses used by the TDP neighbor. Reference: MPLS and VPN Architectures (Ciscopress) page 33 QUESTION 2 The VPN called my_vpn is operating on interface s0/0 of a PE-router. The CE-PE routing protoc

4、ol is RIP. The MPLS backbone IGP is OSPF. How could you verify that the routes received from the remote CE-router are being redistributed into RIP? A. Verify the routing table in the local CE-router. B. Use the show ip cef vrf command on the local PE-router and verify the adjacency table in the CEF

5、cache. C. Use the debug ip routing command in the local PE-router and verify which routes are advertised to the local CE-router. D. Use the show ip routing advertised command on the local PE-router and verify that the routes are being advertised to the CE-router. Answer: A Section: (none) Explanatio

6、n/Reference: Explanation: show ip cef vrf XXX only shows tables on the PE router before redistribution QUESTION 3 Which IOS show command can be used to examine all the routes that have been redistributed into MP-BGP? A. show ip bgp vpnv4 all B. show ip bgp C. show ip route vrf name D. show ip protoc

7、ol vrf name E. show ip route bgp F. show ip bgp sum Answer: A Section: (none) Explanation/Reference: QUESTION 4 The VPN named my_vpn is operating on interface s0/0 of a PE-router. The CE-PE routing protocol is BGP. The MPLS backbone IGP is OSPF. How should you verity routing information is being exc

8、hanged between the PE-routers that support this VPN? A. On the local PE-router, you use the show ip cef vrf command and verify that there is a label for the remote PE-routers 名师资料总结 - - -精品资料欢迎下载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - - - 第 1 页，共 10 页 - - - - - - - - - next-hop. B. On

9、the local PE-router, you use the show ip bgp summary command and verify that the BGP session to the remoter PE-route is up. C. On the local PE-router, you use the show ip bgp vpn4 command and verify that routes from the remote PE-router have been received. D. From the CE-router, you use the pint vrf

10、 command to ping the remote CE-router. If the CE-routers cannot ping each other, then the PE-routers are not exchanging routing information. Answer: C Section: (none) Explanation/Reference: Explanation: To display VPN address information from the BGP tabl, use the show ip bgp vpnv4 command in EXEC m

11、ode. QUESTION 5 What is the purpose of the Down bit in an OSPF LSA header? A. The Down bit is used to prevent redistribution loops between MP-BGP and OSPF. B. The Down bit is used to indicate the route that is being advertised has become unavailable. C. The Down bit is used to indicate an interface

12、has been shut down or become unavailable. D. The Down bit is used to indicate the route that is being advertised is coming from an area that is lower in the hierarchical model. Answer: A Section: (none) Explanation/Reference: QUESTION 6 Exhibit: *MISSING* What is the interaction between the routers

13、in Area 2 and the super-backbone? A. The OSPF super-backbone is completely transparent to OSPF Area 2. B. The super-backbone appears as a BGP domain to the routers in OSPF Area 2. C. The super-backbone appears as another OSPF area to the routers in OSPF Area 2. D. The super-backbone appears as anoth

14、er OSPF domain to the routers in OSPF Area 2. Answer: Section: (none) Explanation/Reference: Explanation: Pending, due to missing exhibit. QUESTION 7 How are routing protocol context implemented in OSPF? A. Each routing context is implemented by redistributing into MBGP. B. Each routing context is i

15、mplemented by assigning it to an interface. C. Each routing context is implemented as a separate routing process. D. Each routing context is implemented as a separate isolated instance of the same routing protocol. Answer: C Section: (none) Explanation/Reference: Explanation: According to the Implem

16、enting Cisco MPLS Student Guide (Text Part Number: 97-1154-01) Volume 2, version 1.0, page 8-6. -Routing context=routing protocol run in one vrf -Routing contexts were introduced in Cisco IOS software to support the need for separate isolated copies of VPN routing protocols. They 名师资料总结 - - -精品资料欢迎下

17、载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - - - 第 2 页，共 10 页 - - - - - - - - - can be implemented as separate routing processes (OSPF), similar to traditional Cisco IOS software implementation, or as separate isolated instances of the same routing protocol (EBGP, RIPv2). This is the same

18、issue as the question 201. QUESTION 8 The VPN named my_vpn is operating on interface s0/0 of a PE-router. The CE-PE routing protocol is OSPF. The MPLS backbone IPG is OSPF. Which statement is true about the interaction between the customers OSPF routes and the backbones OSPF routes? A. On the PE-rou

19、ter, two instances of OSPF are run: one for the VPN and one for the backbone IGP. B. On the PE-router, three instances if OSPF are run: one for the VPN, one for the backbone IGP, and one to carry the PE-PRE routes. C. This configuration is acceptable for MPLS implementations. However, when MPLS VPNs

20、 are implemented, OSPF cannot be used as the CE-PE routing protocol and the backbone IGP. D. On the PE-router, a single instance of OSPF is run. However, the customers routes are kept separate for the backbone route because the RD is prepares to the customers routes. Answer: C Section: (none) Explan

21、ation/Reference: Explanation: It is important to note that the MPLS/VPN backbone is not a real OSPF area 0 backbone. No adjacencies are formed between PE routers - only between PE and CE routers. MP-iBGP is used between PE routers, and all OSPF routes are translated into VPN-IPv4 routes. This means

22、that the redistribution of routes into BGP does not cause these routes to become external OSPF routes when advertised to other member sites of the same VPN. Reference: MPLS and VPN Architectures (Ciscopress) page 235 QUESTION 9 Exhibit: Which statement is true about route summarization for routes an

23、nounced to the backbone by Area 1? A. By default, routes will not be summarized. B. By default, routes will be summarized on the network boundaries. C. By default, routes will be summarized to Area 3 (NSSA) but not to Area 2. D. By default, routes will be summarized based upon the summarization sche

24、dule configured in the CE-router. Answer: B Section: (none) Explanation/Reference: Explanation: Summarizing is the consolidation of multiple routes into one single advertisement. This is normally done at the boundaries of Area Border Routers (ABRs). Although summarization could be configured between

25、 any two areas, it is better to summarize in the direction of the backbone. This way the backbone receives all the aggregate addresses and in turn will injects them, already summarized, into other areas.There are two types of summarization: 1. Inter-area route summarization 1. External route summari

26、zation Reference: http:/ 名师资料总结 - - -精品资料欢迎下载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - - - 第 3 页，共 10 页 - - - - - - - - - QUESTION 10 What is the influence of the Down bit on the OSPF route section process? A. OSPF routes with the Down bit set are never entered in the M-BGP routing table

27、. B. OSPF routes with the Down but set are never entered in the backbones IGP routing table. C. OSPF routes with the Down bit set are passed up the hierarchical model. They are blocked from being passed down the hierarchical model. D. OSPF routes with the Down bit set are marked as unavailable. Afte

28、r the third consecutive update with the Down bit set, they are removed from the routing table. Answer: A Section: (none) Explanation/Reference: Explanation: Customer routes are NEVER entered into the core IGP in an MPLS environment. The down bit does not change this fact. What is does do instead is

29、that it prevent routes redistributes from m-bgp to OSPF from being redistributed back into M-bgp. This makes A the correct answer QUESTION 11 Exhibit: What is the interaction between a super-backbone and Area 3? A. The super-backbone appears as a NSSA to the non-backbone OSPF routers of Area 3. B. T

30、he super-backbone appears as BGP domain to the non-backbone OSPF routers of Area 3. C. The super-backbone appears as another OSPF area to the non-backbone OSPF routers of Area 3. D. The super-backbone appears as Area 0 (backbone area) to the non-backbone OSPF routers of Area 3. Answer: D Section: (n

31、one) Explanation/Reference: Explanation: Traditionally, an elaborate OSPF network consists of a backbone area (area 0) and a number of areas connected to this backbone via an area border router (ABR). By using an MPLS backbone for VPN with OSPF on the customers site, you can introduce a third level

32、in the hierarchy of the OSPF model. This third level is called the MPLS VPN super backbone. In simple cases, the MPLS VPN super backbone is combined with the traditional area 0 backbone. This means that there is no area 0 backbone on the customer network, since the MPLS VPN super backbone plays the

33、same role as the area 0 backbone. This is shown in the diagram below: Reference: http:/ QUESTION 12 How are OSPF route attributes propagates across the MPLS VPN backbone? (Choose two) A. OSPF priority is propagated in the Experimental Bits. B. OSPF cost or external metric is propagated in the BGP ME

34、D attribute. C. Metrics for external OSPF router is propagated in the Hop Count field. D. OSPF area, route type, and metric type are propagated in an extended BGP community. 名师资料总结 - - -精品资料欢迎下载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - - - 第 4 页，共 10 页 - - - - - - - - - Answer: BD Sectio

35、n: (none) Explanation/Reference: Explanation: MP-BGP attaches two new extended community attributes to the routes redistributed from OSPF: * OSPF domain identifier extended community attribute * OSPF route type extended community attribute MP-BGP uses these attributes and the MED to preserve OSPF ro

36、uting information across the BGP/MPLS VPN backbone. Reference: MPLS and VPN Architectures (Ciscopress) page 235 QUESTION 13 Which of the following best describes the function of the OSPF tag field? A. prevents cross-domain routing loops for external LSAs. B. prevents cross-domain routing loops for i

37、nternal LSAs. C. prevents intra-domain routing loops for external LSAs. D. prevents intra-domain routing loops for internal LSAs. Answer: A Section: (none) Explanation/Reference: QUESTION 14 Using OSPF as the CE-PE routing protocol, when and which router will set the down bit? A. The PE router will

38、set the down bit when redistributing routes from MP-BGP into OSPF. B. The PE router will set the down bit when redistributing routes from OSPF into MP-BGP. C. The CE router will set the down bit when propagating the OSPF route to the PE router. D. The PE router will set the down bit when propagating

39、 the OSPF route to the CE router. E. The P router will set the down bit when propagating the route to another P router. F. The PE router will set the down bit when propagating the route to another PE router over MP-BGP. Answer: A Section: (none) Explanation/Reference: QUESTION 15 An OSPF LSA type 5

40、route is redistributed into MP-BGP. That same route is then redistributed back from MP-BGP into OSPF on another PE router. In this case, that OSPF route will appear as what LSA type on the destination CE router? A. LSA type 1 B. LSA type 2 C. LSA type 3 D. LSA type 4 E. LSA type 5 F. LSA type 7 Answ

41、er: E Section: (none) Explanation/Reference: QUESTION 16 The VPN named my_vpn is operating on interface s0/0 of a PE-router. The CE-PE routing protocol is OSPF. Why is the OSPF super-backbone needed in MPLS VPN environments? 名师资料总结 - - -精品资料欢迎下载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - -

42、 - 第 5 页，共 10 页 - - - - - - - - - A. To ensure that the customers OSPF traffic has priority over the backbone OSPF routing updates. B. To ensure that the backbone internal OSPF routes are not inserted as external OSPF routes into the customers VPN. C. To ensure that the customers internal OSPF route

43、s on one site are not inserted as external OSPF routes into other sites on the same VPN. D. To ensure that the customers internal OSPF routes are not inserted as external OSPF routes into the provider backbone as internal OSPF routes. Answer: C Section: (none) Explanation/Reference: QUESTION 17 In C

44、isco IOS release 12.1, how many VPN OSPF process can run simultaneously in an MPLS VPN PE-router? A. 1. B. 28 C. 255 D. The number of active processes is controlled by the memory available. Answer: B Section: (none) Explanation/Reference: QUESTION 18 Which three statements about the traditional OSPF

45、 routing model are true? (Choose three) A. Networks running OSPF can be divided into areas. B. OSPF was designed to support hierarchical networks. C. A single area is a physical site or logical division of that site. D. All areas must be physically connected to the backbone area (Area 0) E. OSPF imp

46、lementations consisting of multiple areas must be interconnected by a backbone area. Answer: ABE Section: (none) Explanation/Reference: Explanation: Not C: The area in traditional OSPF is a logical union of routers Not D: It is highly recommended that all areas are connected to the backbone are, but

47、 it is not obligatory. Using virtual link the area can be just logically be connected to the area 0. QUESTION 19 BGP address families are used to configure which three route exchange mechanisms? (Choose three) A. Propagating Internet routes. B. VPNv4 routes that are propagated across an MPLS/VPN bac

48、kbone. C. P-router to P-router routes that are propagated across an MPLS/VPN backbone. D. PE-CE routing protocol to exchange VPN routes between provider edge routers and customer edge routers. Answer: ABD Section: (none) Explanation/Reference: Explanation: According to the Implementing Cisco MPLS St

49、udent Guide (Text Part Number: 97-1154-01) Volume 2, version 1.0, page 8-31. BGP address families: The BGP process in a MPLS VPN-enabled router performs 3 separate tasks: - Global BGP routes(internet routing) are exchanged as in traditional BGP setup. - VPNv4 prefixes are exchanged through MP-BGP. 名

50、师资料总结 - - -精品资料欢迎下载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - - - 第 6 页，共 10 页 - - - - - - - - - - VPN routes are exchanged with CE routers through per-VRF EBGP sessions. Address families (routing contexts) are used to configure these three tasks in the same BGP process(because only one B