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OSPF Questions

July 20th, 2011 in ROUTE 642-902 Go to comments

Here we will find answers to OSPF questions

Question 1

An administrator Pipes in the command router ospf 1 and receives the error message: “OSPF process 1 cannot start.” (Output is omitted.) What should be done to correctly set up OSPF?

A – Ensure that an interface has been configured with an IP address
B – Ensure that an interface has been configured with an IP address and is up
C – Ensure that IP classless is enabled
D – Ensure that the interfaces can ping their directly connected neighbors


Answer: B

Question 2

During a recent OSPF election among three routers. RTA was elected the DR and RTB was elected the BDR, as seen in the graphic. Assume that RTA fails, and that RTB takes the place of the DR while RTC becomes the new BDR. What will happen when RTA comes back online?

OSPF_DR_DBR

A – RTA will take the place of DR immediately upon establishing its adjacencie
B – RTA will take the place of DR only if RTB fails
C – RTA will take the place of DR only if both RTB and RTC fail
D – A new election will take place establishing an all new DR and BDR based on configured priority levels and MAC addresses


Answer: C

Question 3

Refer to the exhibit. During the process of configuring a virtual link to connect area 2 with the backbone area, the network administrator received this console message on R3:
*Mar 1 00:25:01.084: %OSPF-4-ERRRCV: Received invalid packet: mismatch area ID, from backbone area must be virtual link but not found from 20.20.20.1, Serial 0

How should the virtual link be configured on the OSPF routers to establish full connectivity between the areas?

OSPF_virtual_link

A – R1(config-router)# area 1 virtual-link 30.30.30.3
R3(config-router)# area 1 virtual-link 20.20.20.1
B – R1(config-router)# area 1 virtual-link 20.20.20.2
R3(config-router)# area 1 virtual-link 30.30.30.2
C – R1(config-router)# area 0 virtual-link 1.1.1.1
R3(config-router)# area 2 virtual-link 3.3.3.3
D – R1(config-router)# area 1 virtual-link 3.3.3.3
R3(config-router)# area 1 virtual-link 1.1.1.1
E – R1(config-router)# area 1 virtual-link 2.2.2.2
R3(config-router)# area 1 virtual-link 2.2.2.2

Answer: D

Explanation

When designing a multi-area OSPF network, all areas should be connected to the backbone area. However, there may be instances when an area will need to cross another area to reach the backbone area like area 2 in this case. A virtual link has the following two requirements:

+ It must be established between two routers that share a common area and are both ABRs.
+ One of these two routers must be connected to the backbone.

In this case, two routers that satisfy the above requirements are R1 and R3. The syntax for creating a virtual link across an area is:

area area-id virtual-link neighbor-router-id

The area-id is the number of the transit area, in this example Area 1 and neighbor-router-id is the IP address of the highest loopback interface configured or can be manually set on the neighboring router.

Question 4

As shown in the exhibit ,OSPF is configured over a Frame Relay network. All PVCs are active. However, P4S1 and P4S3 fail to see all OSPF routes in their routing tables. The show ip ospf neighbor command executed on P4S2 displays the state of the neighbors. In order to fix the problem , what should be done?

OSPF_NBMA_Frame_Relay

A – The neighbor command should be configured under the OSPF routing process on all routers
B – The ip ospf network broadcast command should be configured on each Frame Relay interface
C – The ip ospf network non-broadcast command should be configured on each Frame Relay interface
D – The ip ospf priority value on the spoke routers should be set to 0


Answer: D

Explanation

In an NBMA network topology, neighbors are not discovered automatically. OSPF tries to elect a DR and a BDR due to the multi-access nature of the network, but the election fails since neighbors are not discovered because NBMA environment doesn’t forward broadcast and multicast packets. Neighbors must be configured manually to overcome these problems.

Also, additional configuration is necessary in a hub and spoke topology to make sure that the hub routers, which have connectivity with every other spoke router, are elected as the DR and BDR. You must set the spoke interfaces to an OSPF priority of zero, this ensures that the spokes will not become the DR or BDR.

Question 5

The following exhibit shows ipv6 route output. What would the metric be for a summary route that summarizes all three OSPFv3 routes displayed?

cost_of_summary_route

A – 160
B – 140
C – 120
D – 100


Answer: D

Explanation

The cost of the summarized routes is the highest cost of the routes being summarized. In fact, in the old RFC 1583 standard, the cost of the summary route was the cost of the lowest metric. But when OSPF was updated in RFC 2178 and RFC 2328, the summary route should have the same cost as the highest-cost summarized route. In this case, the highest-cost is 100 according to the second entry.

Question 6

Study the exhibit below carefully. In order to summarize all routes from area 0 to area 1, what must be configured on the router?

area_range_summary_OSPF

A – area 0 range 172.16.96.0 255.255.224.0
B – area 1 range 172.16.96.0 255.255.224.0
C – area 1 range 172.16.96.0 255.255.0.0
D – area 0 range 172.16.96.0 255.255.255.0


Answer: A

Comments
Comment pages
1 2 19
  1. Alex Ivanov
    January 4th, 2012

    I think in question 6 the answer should be B.

  2. Alex Ivanov
    January 5th, 2012

    Oh, sorry. Answer A is correct, ofcourse.

  3. Sir CCNP
    January 18th, 2012

    Hello Friends,

    I just started to study the ROUTE test after taking almost two years off from passing the CCNA. I am planning to take the ROUTE test in two months. Are the Sims, Drag and Drop, Questions, and everything else on this site still valid for the ROUTE test?

    Thank you all!

  4. michael
    February 5th, 2012

    i really want to use this opportunity to say thank u to the DIGITALTUT team for puttin all this together , and my various friends as well u are not left behinde ,atleast for ur contributions

  5. NARESH
    February 26th, 2012

    VERY GOOD ANSWER

  6. Kalpana
    February 29th, 2012

    For some reosan this sounds familiar to me wasn’t it designed by the same designer my colleague worked with on certain customer’s network? Seriously, he showed me very similar setup to this. One non-backbone stub area with 4 or so routers (to minimize traffic and processing from OSPF), made as NSSA (to be able to redistribute couple of connected routes to/from BGP). We were all just shaking our heads. I do not remember if he managed to talk him away from this nonsense

  7. Sisjun
    March 25th, 2012

    Hello,
    Question – What are OSPF ABR functions (Choose three)
    - flooding Summary LSAs to connected areas?
    - flooding ASBR Summary LSAs to connected areas?
    - flooding NSSA External LSAs to Area 0?
    - performing summarization on routes headed to Area 0?
    - Generating all Router LSAs for connected neighbors?
    Thanks!

  8. venkat
    April 21st, 2012

    i think first 3 statements are correct

  9. ie3
    May 4th, 2012

    Hi guys,

    Is it true we can skip all Frame Relay and NBMA questions?

  10. JOHN
    May 20th, 2012

    Q 6 is incorrect

    summary address shoulde be
    255.255.128.0 coz 01100000 to
    01111111
    Please correct me if m wrong

  11. Jay
    May 20th, 2012

    Question 6 is correct.

    Your summary boundary is established where the bit pattern in your range of network addresses changes. All networks summarized will have the same network portion. In this example the change takes place at the 20th bit, making the first 19 bits the same:

    011 00000
    011 11111

    Therefore 255.255.224.0 is the correct mask for this example.

  12. Raj
    June 5th, 2012

    When a router analyzes the OSPF LSDB to calculate the best route to each subnet for internal
    routes, it does the calculations in a specific order. Which answer below puts the calculations in
    the correct order of operation?
    Choose the best answer.
    A. 1. Calculates the OSPF interface costs for all outgoing interfaces in each route, picking the
    lowest total cost route for each subnet as the best route.
    2. Finds all subnets inside the area, based on the stub interfaces listed in the Type 1 LSAs and
    based on any Type 2 network LSAs.
    3. Runs SPF to find all possible paths through the area’s topology, from itself to each subnet.
    B. 1. Finds all subnets inside the area, based on the stub interfaces listed in the Type 1 LSAs
    and based on any Type 2 network LSAs.
    2. Runs SPF to find all possible paths through the area’s topology, from itself to each subnet.
    3. Calculates the OSPF interface costs for all outgoing interfaces in each route, picking the
    lowest total cost route for each subnet as the best route.
    C. 1. Finds all subnets inside the area, based on the stub interfaces listed in the Type 1 LSAs
    and based on any Type 2 network LSAs.
    2. Calculates the OSPF interface costs for all outgoing interfaces in each route, picking the
    lowest total cost route for each subnet as the best route.
    3. Runs SPF to find all possible paths through the area’s topology, from itself to each subnet.
    D. 1. Runs SPF to find all possible paths through the area’s topology, from itself to each
    subnet.
    2. Finds all subnets inside the area, based on the stub interfaces listed in the Type 1 LSAs and
    based on any Type 2 network LSAs.
    3. Calculates the OSPF interface costs for all outgoing interfaces in each route, picking the
    lowest total cost route for each subnet as the best route.

    what should be answer?? anybody?? pls

  13. Dejan
    June 5th, 2012

    @Raj

    Answer is C. OSPF router must first analyze its LSDB (find all subnets), calculate its own interface cost using 10^8/bandwidth formulae and then run SPF algorithm to find all possible paths.

  14. Raj
    June 7th, 2012

    @Dejan: Thank you :)

  15. Brody99
    July 9th, 2012

    Can somebody please confirm rumors on a different site this hotspot is no longer part of the exam? Thanks.

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    August 20th, 2012

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  18. Mawarr
    August 24th, 2012

    Dear Careercert, I am very thankful for prdioving All Cisco videos, and i am very thankful to Jeremy expecially .. His voice is gods gift , i am very much excited with CCNP videos, thanks once again. I need Jeremy’s E-mail please, So that i can ask some in debth videos of Redistriburion and IP SLA of , because recently i started BSCI study . So, Please , Jeremy can you help me regarding these video, and send me a link .I am very thankful to you.. Our faculy is not able to teach Redistriburion and IP SLA chapters , and even Lab also not good. So please help me..

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  20. Me
    September 29th, 2012

    @Raj; Dejan

    I believe the answer is B. The OSPf process firstly, finds the subnets in its area, then it finds all possible paths from itself to the subnets found before it can determine the best paths by calculating each path together with its interface metric.

  21. Mrityunjay singh
    October 15th, 2012

    Is all the questions on digitaltut is latest….?

  22. Ccnpnew
    November 16th, 2012

    For question 3 – how can answer D be correct since router 1and router 3 cannot be neighbors? Isn’t it true that neighbors must have interfaces on the same link? I believe answer E is correct.

  23. Ccnpnew
    November 16th, 2012

    For question 3 D is correct. Sorry. When configuring a virtual link you must specify the router ID of the far end router of the transit area. The far end router is the ABR linking the transit area to the area the virtual link is connecting.

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  25. Jamerican
    February 10th, 2013

    Is the diagram labeled incorrectly in #3 to have area 0 to the left instead of the center ring?

  26. kel
    February 11th, 2013

    @ all, on question # 2, pls help me on the answer, cause I think it should be A, Ive tried tested this on PT , and after I shut down Router A, as expected Router B and Router C assumes their respective roles. but after you make Router A operational , as soon as it establishes adjacency, it immediately assumes the role of DR. I taught that DR/BDR election is not pre- empted but my tests shows different.

    thanks in advance.!

  27. kel
    February 13th, 2013

    hi, regarding Q#2, I’ve retested it in GNS3 and I must admit that A was not the answer due to inconsistencies on my config. sorry folks, but then indeed “C” was the best answer but take note that if Router B and Router C is down, then no neighbor adjacency will be formed on Router A, so basically Router A is not a DR, since no neighbor is up. thanks,!

  28. JL
    March 14th, 2013

    @kel

    Answer C is correct,

    No matter what the IP of the routers are or how many Loopback interface there is, once router A starts it will become the BDR then DR because is the only router. However when the second router comes into play, the B router will be selected as BDR and Router A will be DR because it was the first router on line up. When the C router comes in it will be selected as DROTHER because DR/BDR is already elected and they will not preempt. The election process will not start unless one of the DR/BDR is down. they will have another election which is to replace the BDR. It will not replace the position of the DR because the original BDR will be automatically elected as DR. Until both router B & C is down router A won’t be elected as DR.

    Hope this helps

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  32. Hi_ROUTE
    July 25th, 2013

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    Exam duration is 2.5 hours, so take your time, think and complete your exam in no hurry.
    IP addresses have changed, the option’s order has changed so be patient and careful, while selecting the answer.

    The simulators don’t support neither “wr” nor “copy running-config start-config”, except an OSPF sim which is about “stub”.

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    August 25th, 2013

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