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ICND2 – OSPF Questions

April 25th, 2015 in ICND2 200-101 Go to comments

Note: If you are not sure about OSPF, please read my OSPF tutorial first.

Question 1

Explanation

First, notice that the more-specific routes will always be favored over less-specific routes regardless of the administrative distance set for a protocol. In this case, because we use OSPF for three networks (172.16.100.0 0.0.0.3, 172.16.100.64 0.0.0.63, 172.16.100.128 0.0.0.31) so the packets destined for these networks will not be affected by the default route.

The default route configured on R1 “ip route 0.0.0.0 0.0.0.0 serial0/0″ will send any packet whose destination network is not referenced in the routing table of router R1 to R2, it doesn’t drop anything so answers A, B and C are not correct. D is not correct too because these routes are declared in R1 and the question says that “OSPF has been correctly configured on router R2″, so network directly connected to router R2 can communicate with those three subnetworks.

As said above, the default route configured on R1 will send any packet destined for a network that is not referenced in its routing table to R2; R2 in turn sends it to R1 because it is the only way and a routing loop will occur.

Question 2

Explanation

Link-state protocol uses hello packets to discover neighbors and establish adjacencies. After that, the routers begin sending out LSAs to every neighbor (each received LSA is copied and forwarded to every neighbor except the one that sent the LSA)

Question 3

Question 4

Explanation

The Administrative Distances (AD) of popular routing protocols are listed below:

Administrative Distances_popular_routing_protocols.jpg

Question 5

Explanation

Router_E learns two subnets subnets 208.149.23.64 and 208.149.23.96 via Router_A through FastEthernet interface. The interface cost is calculated with the formula 108 / Bandwidth. For FastEthernet it is 108 / 100 Mbps = 108 / 100,000,000 = 1. Therefore the cost is 12 (learned from Router_A) + 1 = 13 for both subnets -> B is not correct.

The cost through T1 link is much higher than through T3 link (T1 cost = 108 / 1.544 Mbps = 64; T3 cost = 108 / 45 Mbps = 2) so surely OSPF will choose the path through T3 link -> Router_E will choose the path from Router_A through FastEthernet0/0, not Serial1/0 -> C & D are not correct.

In fact, we can quickly eliminate answers B, C and D because they contain at least one subnet learned from Serial1/0 -> they are surely incorrect.

Question 6

Explanation

OSPF is a link-state routing protocol so it converges more quickly than distance-vector protocol. OSPF uses cost to determine the best route. The popular formula to calculate OSPF cost is: cost = 108 / Bandwidth [ in kbps] (in fact the formal formula is: cost = reference bandwidth / configured bandwidth of interface in kbps. On Cisco routers, the reference bandwidth defaults to 100000 kbps)

Question 7

Explanation

There are 2 segments on the topology above which are separated by Corp-3 router. Each segment will have a DR so we have 2 DRs.

To select which router will become DR they will compare their router-IDs. The router with highest (best) router-ID will become DR. The router-ID is chosen in the order below:

+ The highest IP address assigned to a loopback (logical) interface.

+ If a loopback interface is not defined, the highest IP address of all active router’s physical interfaces will be chosen.

In this question, the IP addresses of loopback interfaces are not mentioned so we will consider IP addresses of all active router’s physical interfaces. Router Corp-4 (10.1.40.40) & Branch-2 (10.2.20.20) have highest “active” IP addresses so they will become DRs.

Question 8

Explanation

The well-known formula to calculate OSPF cost is

Cost = 108 / Bandwidth

so B is the correct answer.

Question 9

Explanation

The default-information originate command advertises a default route to other routers, telling something like “please send me your unknown traffic”. So in this case, besides a full routing table, R2 will also receive a default route from R1 -> B is correct.

Note: But in this question, the static route should be “ip route 0.0.0.0 0.0.0.0 serial0/1″ (not serial0/0), that may cause a routing loop.

Question 10

Explanation

In the router ospf command, the ranges from 1 to 65535 so o is an invalid number -> B is correct but A is not correct.

 

Comments (30) Comments
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  1. SN
    October 11th, 2015

    Question 9 note is incorrect as the interface is mentioned as an exit interface of router 1 as it should be. But B option appears correct

  2. Texas
    October 12th, 2015

    Q9 answer Router R2 will not form a neighbor relationship with R1/ I got 1000/1000

  3. Paul
    November 4th, 2015

    I cannot see the questions, only the answers and explanations.

  4. Girvan
    November 19th, 2015

    Why would Router 2 not form a neighbour relationship?

  5. Anon
    December 4th, 2015

    9tut Question 9 correct answer is A

  6. me2
    December 21st, 2015

    @Texas

    But the routers WOULD form a neighbour relationship! Try it in packet tracer.

    Answer is definitely B, I didn’t get asked this question but passed with 980. I would have picked B if it had come up.

  7. jongililo
    February 25th, 2016

    Are these dumps still valid?

  8. Epema
    March 30th, 2016

    Hi, coud you give more details on question 7?
    What is meant by network segment? Why there are two segments and why they are separated by Corp-3 router?

  9. Anonymous
    April 8th, 2016

    Question 9.

    >Line 1 indicates that all unknown routes will exit R1 via S0/0.
    >Line 6 propogates the default route configured in Line 1, into OSPF.
    >When the default route is propogated into OSPF, the exit interface will change to the IP Address of that interface.
    >Any address not in R1’s routing table will be sent out its S0/0 interface.
    >Once R2 gets it, it will send out to the IP Address of R1’s S0/0 interface.
    >Once R1 gets it back, it will notice that the source IP is one of its interfaces IP, it will drop the packet.

  10. mani
    May 9th, 2016

    I think there is a problem in Q 1.
    You are saying A,B,C and D are not correct, but we have only one option with the explanation statement and that is option B. ((“routing loop will occur”. ))

    Please correct me if I am wrong.

  11. MIKE
    May 12th, 2016

    I HAD TODAY Q1,4,6,8,9
    AT Q.9 I CHOOSE A…. BUT I THINK THAT WAS WRONG… THIS WAS THE ONLY QUES. I GOT HESITATED…I GOT 986/1000..SO THIS MAY BE THE ONLY MISTAKE AT MY EXAM…
    IF IT COME TO YOU GO FOR B…..ITS BETTER ANSWER…

  12. Euro2016
    June 13th, 2016

    Welp, I’ll be taking the ICND2 in a couple of weeks. I think I’ll go with A for Q9.

  13. Gj
    June 20th, 2016

    Q7.

    It should be C & F. Corp-3 should be DR for its segment because it’s attached to Branch-1, which will make Corp-3’s serial ip something like, 10.2.10.9. Although the serial link won’t have a DR, Corp-3’s serial ip will be Corp-3’s RID, thus making it higher than all the other Corp routers. Remember, a router will use the highest ip on it, unless it’s a loopback.

  14. Ghayth
    July 2nd, 2016

    Q9: the answer is A

    Because the AREA is 0 while router 1 in configured in Area 1 so for sure Router R2 will not form a neighbour relationship with R1.

  15. Hank
    July 13th, 2016

    @Ghayth
    R1 is not configured in Area 1. The ‘1’ referred to in the output is the data base instance and can be any number. It is a local number on any router and is also called a process number.

  16. Anonymous
    July 19th, 2016

    guys help am taking my exam in 2 days,are this questions still on the exam.

  17. me2
    August 5th, 2016

    Just passed CCNP and came back to check here for new opinions on Q9.

    LOL if you pick A for Q9 you are getting it wrong. Confirmed by Keith Barker of Nuggets and every networking lecturer I have spoken to.

    Good Luck

  18. Anonymous
    August 10th, 2016

    i cannot see the questions, only explanation for answer.
    Please some one share the link of the questions

  19. Karena
    September 1st, 2016

    After testing with packet tracer (though not a very good sim) and reading many dumps on this question with explanations, I believe that the answer of Question 9 should be A.
    First, please note that the static route command is input before the ospf command, which would cause a loop and congestion between R1 and R2.
    Therefore, when later ospf 1 is set, ospf cannot perform relationship between them.

  20. Wayne Burn Bayby Burn !
    September 5th, 2016

    Q.1 Assuming that all router interfaces are operational and correctly configured, that OSPF has
    been correctly configured on router R2, how will the default route configured on R1 affect
    the operation of R2?

    Answer – B. Any packet destined for a network that is not referenced in the routing table of router R2 will be directed to R1. R1 will then send that packet back to R2 and a routing loop will occur.

    Q.9 Assume that all of the router interfaces are operational and configured correctly. How will
    router R2 be affected by the configuration of R1 that is shown in the exhibit?
    Answer – A. Router R2 will not form a neighbor relationship with R1.

  21. CCIE
    September 10th, 2016

    question 9 is B

  22. harry£
    September 11th, 2016

    question is 9 contraversia! can sombody please confirm what should be the answer?? i got exam tomorrow

  23. yarp
    September 16th, 2016

    For an explanation on q9 just look at q10.
    “In the router ospf command, the ranges from 1 to 65535 so 0 is an invalid number”
    So for q9 the correct answer is B

  24. Syn
    September 18th, 2016

    So with Q9 is this not B?

  25. scoofi
    September 20th, 2016

    is B o Is A????

  26. answer this
    September 20th, 2016

    answer cannot be A! ospf process is 1 not 0.

  27. randal
    September 22nd, 2016

    does anyone still have a the q/a these pages refer to? or the most up to date dump for 200-201?
    r a n d a l t h o r z @ p r o t o n m a i l . c o m
    ty

  28. Lucas
    September 22nd, 2016

    Question 9 is A. Just passed 1000/1000 (22.09.2016)

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    January 10th, 2017

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  30. Sg
    March 6th, 2017

    Are all these dumps valid? I am planning to give my exam on 20th march

Comment pages
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