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OSPF Neighbor Sim

October 6th, 2014 Go to comments

Question

The topology below is running OSPF. You are required to troubleshoot and resolve the OSPF issues between the various routers. Use the appropriate show commands to troubleshoot the issues.

OSPF_Neighbor_Sim.jpg

Instead of posting the output of “show run” commands we post here the commands entered on each router to reduce some useless lines. Also you can try solving questions by yourself before reading the answers.

R1
interface Loopback0
 description ***Loopback***
 ip address 192.168.1.1 255.255.255.255
 ip ospf 1 area 0
!
interface Ethernet0/0
 description **Connected to R1-LAN**
 ip address 10.10.110.1 255.255.255.0
 ip ospf 1 area 0
!
interface Ethernet0/1
 description **Connected to L2SW**
 ip address 10.10.230.1 255.255.255.0
 ip ospf hello-interval 25
 ip ospf 1 area 0
!
router ospf 1
 log-adjacency-changes

R2
!
interface Loopback0
 description **Loopback**
 ip address 192.168.2.2 255.255.255.255
 ip ospf 2 area 0
!
interface Ethernet0/0
 description **Connected to R2-LAN**
 ip address 10.10.120.1 255.255.255.0
 ip ospf 2 area 0
!
interface Ethernet0/1
 description **Connected to L2SW**
 ip address 10.10.230.2 255.255.255.0
 ip ospf 2 area 0
!
router ospf 2
 log-adjacency-changes
R3
username R6 password CISCO36
!
interface Loopback0
 description **Loopback**
 ip address 192.168.3.3 255.255.255.255
 ip ospf 3 area 0
!
interface Ethernet0/0
 description **Connected to L2SW**
 ip address 10.10.230.3 255.255.255.0
 ip ospf 3 area 0
!
interface Serial1/0
 description **Connected to R4-Branch1 office**
 ip address 10.10.240.1 255.255.255.252
 encapsulation ppp
 ip ospf 3 area 0
!
interface Serial1/1
 description **Connected to R5-Branch2 office**
 ip address 10.10.240.5 255.255.255.252
 encapsulation ppp
 ip ospf hello-interval 50
 ip ospf 3 area 0
!
interface Serial1/2
 description **Connected to R6-Branch3 office**
 ip address 10.10.240.9 255.255.255.252
 encapsulation ppp
 ip ospf 3 area 0
 ppp authentication chap
!
router ospf 3
 router-id 192.168.3.3
!
R4
!
interface Loopback0
 description **Loopback**
 ip address 192.168.4.4 255.255.255.255
 ip ospf 4 area 2
!
interface Ethernet0/0
 ip address 172.16.113.1 255.255.255.0
 ip ospf 4 area 2
!
interface Serial1/0
 description **Connected to R3-Main Branch office**
 ip address 10.10.240.2 255.255.255.252
 encapsulation ppp
 ip ospf 4 area 2
!
router ospf 4
 log-adjacency-changes
R5
!
interface Loopback0
 description **Loopback**
 ip address 192.168.5.5 255.255.255.255
 ip ospf 5 area 0
!
interface Ethernet0/0
 ip address 172.16.114.1 255.255.255.0
 ip ospf 5 area 0
!
interface Serial1/0
 description **Connected to R3-Main Branch office**
 ip address 10.10.240.6 255.255.255.252
 encapsulation ppp
 ip ospf 5 area 0
!
router ospf 5
 log-adjacency-changes
R6
username R3 password CISCO36
!
interface Loopback0
 description **Loopback**
 ip address 192.168.6.6 255.255.255.255
 ip ospf 6 area 0
!
interface Ethernet0/0
 ip address 172.16.115.1 255.255.255.0
 ip ospf 6 area 0
!
interface Serial1/0
 description **Connected to R3-Main Branch office**
 ip address 10.10.240.10 255.255.255.252
 encapsulation ppp
 ip ospf 6 area 0
 ppp authentication chap
!
router ospf 6
 router-id 192.168.3.3
!

Note: Packet Tracer does not support enabling OSPF under interface mode (ip ospf 3 area 0). We don’t know why such a popular command is not supported so we can’t make a pkt file for this lab.

Question 1

Explanation

We learned it is a OSPF problem so we should check the interfaces between them first. On both R3 and R4 use “show running-config” command to check their S1/0 interfaces

R3#show running-config
<<output omitted>>
!
interface Serial1/0
  description **Connected to R4-Branch1 office**
  ip address 10.10.240.1 255.255.255.252
  encapsulation ppp
  ip ospf 3 area 0
!
<<output omitted>>
R4#show running-config
<<output omitted>>
!
interface Serial1/0
  description **Connected to R3-Main Branch office**
  ip address 10.10.240.2 255.255.255.252
  encapsulation ppp
  ip ospf 4 area 2
!
<<output omitted>>

In the output above we see their Area IDs are mismatched; interface S1/0 of R3 is in area 0 (R3: ip ospf 3 area 0) while interface s1/0 of R4 is in area 2 (R4: ip ospf 4 area 2).

Question 2

Explanation

Continue checking their connected interfaces with the “show running-config” command:

R3#show running-config
<<output omitted>>
!
interface Serial1/1
  description **Connected to R5-Branch2 office**
  ip address 10.10.240.5 255.255.255.252
  encapsulation ppp
  ip ospf hello-interval 50
  ip ospf 3 area 0
!
<<output omitted>>
R5#show running-config
<<output omitted>>
!
interface Serial1/0
  description **Connected to R3-Main Branch office**
  ip address 10.10.240.6 255.255.255.252
  encapsulation ppp
  ip ospf 5 area 0
!
<<output omitted>>

The only difference we can see here is the line “ip ospf hello-interval 50” on R3. This command sets the number of seconds R3 waits before sending the next hello packet out this interface. In this case after configuring this command, R3 will send hello packets to R5 every 50 seconds. But the default value of hello-interval is 10 seconds and R5 is using it. Therefore we can think of a hello interval mismatch problem here. You can verify with the “show ip ospf interface <interface>” command on each router.

R3#sh ip ospf int s1/1
Serial1/1 is up, line protocol is up
  Internet Address 10.10.240.5/30, Area 0
  Process ID 3, Router ID 192.168.3.3, Network Type POINT_TO_POINT, Cost: 64
  Enabled by interface config, including secondary ip addresses
  Transmit Delay is 1 sec, State POINT_TO_POINT,
  Timer intervals configured, Hello 50, Dead 200, Wait 200, Retransmit 5
  oob-resync timeout 200
  Hello due in 00:00:28
  Supports Link-local Signaling (LLS)
  Index 2/2, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 0, maximum is 0
  Last flood scan time is 0 msec, maximum is 0 msec
  Neighbor Count is 0, Adjacent neighbor count is 0
  Suppress hello for 0 neighbor(s)
R5#sh ip ospf int s1/0
Serial1/0 is up, line protocol is up
  Internet Address 10.10.240.6/30, Area 0
  Process ID 5, Router ID 10.10.240.6, Network Type POINT_TO_POINT, Cost: 64
  Enabled by interface config, including secondary ip addresses
  Transmit Delay is 1 sec, State POINT_TO_POINT,
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
  oob-resync timeout 40
  Hello due in 00:00:04
  Supports Link-local Signaling (LLS)
  Index 1/1, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 0, maximum is 0
  Last flood scan time is 0 msec, maximum is 0 msec
  Neighbor Count is 0, Adjacent neighbor count is 0
  Suppress hello for 0 neighbor(s)

So we can see both hello and dead interval are mismatched because the dead interval always four times the value of hello interval, unless you manually configure the dead interval (with the ip ospf dead-interval <seconds> command).

Question 3

Explanation

Continue checking their connected interfaces with the “show running-config” command:

R1#show running-config
<<output omitted>>
!
interface Ethernet0/1
  description **Connected to L2SW**
  ip address 10.10.230.1 255.255.255.0
  ip ospf hello-interval 25
  ip ospf 1 area 0
!
<<output omitted>>
R2#show running-config
<<output omitted>>
!
interface Ethernet0/1
  description **Connected to L2SW**
  ip address 10.10.230.2 255.255.255.0
  ip ospf 2 area 0
!
<<output omitted>>

We see the hello interval on R1 is not the same as R2 (and you can verify with the “show ip ospf interface <interface> command”) -> There is a hello and dead interval mismatch problem. We should configure “no ip ospf hello-interval 25” on R1.

Note: Maybe there are some versions of this question in the exam. For example there are some reports saying that Ethernet0/1 on R1 is shutdown (and this is the correct choice in the exam). So please be careful checking the config on the routers before choosing the correct answers.

Question 4

Explanation

R3#show running-config
<<output omitted>>
username R6 password CISCO36
!
interface Serial1/2
  description **Connected to R6-Branch3 office**
  ip address 10.10.240.9 255.255.255.252
  encapsulation ppp
  ip ospf 3 area 0
  ppp authentication chap
!
<<output omitted>>
!
router ospf 3
  router-id 192.168.3.3
!
<<output omitted>>
R6#show running-config
<<output omitted>>
username R3 password CISCO36
!
interface Serial1/0
  description **Connected to R3-Main Branch office**
  ip address 10.10.240.10 255.255.255.252
  encapsulation ppp
  ip ospf 6 area 0
  ppp authentication chap
!
<<output omitted>>
!
router ospf 6
  router-id 192.168.3.3
!
<<output omitted>>

We are not sure about the configuration of ppp authentication in this case. Some reports said that only one router has the “ppp authentication chap” command but it is just a trick and is not the problem here. The real problem here is R6 uses the same router-id of R3 (192.168.3.3) so OSPF neighborship cannot be established. In real life, such configuration error will be shown in the command line interface (CLI). So please check carefully for this question.

Comments (36) Comments
Comment pages
1 17 18 19 2243
  1. anin
    January 12th, 2017

    wheres the questions? help please

  2. abc
    January 12th, 2017

    wheres the questions? i can’t view the questions help please

  3. Nasser
    January 14th, 2017

    wheres the questions? help please

  4. Marry
    January 17th, 2017

    guys, how can i practice for OSPF Sim, since the topology from 9tut is not downloadable (“Packet Tracer does not support enabling OSPF under interface mode (ip ospf 3 area 0)” )
    Thank you!

  5. on1
    January 29th, 2017

    To view the questions I had to time travel….

    #https#:/#/#web#.archive.#org#/web#/20150210235537#/#http#:/#/ww#w.9tut.#co#m/ospf-neighbor-sim

    remove all # from link

  6. sheff07
    February 9th, 2017

    thanks on1

  7. Sulabh
    February 9th, 2017

    @on1 Hi the link is not working.

  8. Sulabh
    February 9th, 2017

    @on1 thanks it works can you give give link to eigrp sim questions?

  9. iks
    February 11th, 2017

    ,k,

  10. Anonymous
    February 12th, 2017

    Can anyone please email me the questions and options of these explanations ?
    kindly mail me on this email address kamiwazir6 @ gmail.com

  11. jmachado
    February 16th, 2017

    I have made a packet tracer activity for this project. Keep in mind that you must go to Cisco Academy and download/install packet tracer 7 (Sign up, it’s a free download). Older versions of PT does not support OSPFv3 for IPv4. Again, 9tut may use this on their web page.

    http ://
    bit . ly / 2lORYgL

  12. versace
    February 17th, 2017

    jmachado you are the man!!

  13. SHAH indian
    February 18th, 2017

    those who are wondering where are the questions, dont worry i am here :p

    Question 1
    An OSPF neighbor adjacency is not formed between R3 in the main office and R4 in the Branch1 office. What is causing the problem?
    A. There is an area ID mismatch. B. There is a Layer 2 issue; an encapsulation mismatch on serial links. C. There is an OSPF hello and dead interval mismatch. D. The R3 router ID is configured on R4.
    Answer: A

    Question 2
    An OSPF neighbor adjacency is not formed between R3 in the main office and R5 in the Branch2 office. What is causing the problem?
    A. There is an area ID mismatch. B. There is a PPP authentication issue; a password mismatch.
    C. There is an OSPF hello and dead interval mismatch. D. There is a missing network command in the OSPF process on R5.
    Answer: C

    Question 3
    R1 does not form an OSPF neighbor adjacency with R2. Which option would fix the issue?
    A. R1 ethernet0/1 is shutdown. Configure no shutdown command. B. R1 ethernet0/1 configured with a non-default OSPF hello interval of 25; configure no ip ospf hello-interval 25 C. R2 ethernet0/1 and R3 ethernet0/0 are configured with a non-default OSPF hello interval of 25; configure no ip ospf hello-interval 25 D. Enable OSPF for R1 ethernet0/1; configure ip ospf 1 area 0 command under ethernet0/1
    Answer: B

    Question 4
    An OSPF neighbor adjacency is not formed between R3 in the main office and R6 in the Branch3 office. What is causing the problem?
    A. There is an area ID mismatch. B. There is a PPP authentication issue; the username is not configured on R3 and R6. C. There is an OSPF hello and dead interval mismatch. D. The R3 router ID is configured on R6.
    Answer: D

    all the best & remember me in your prayers

  14. Anonymous
    February 20th, 2017

    thanks shah

  15. silky
    February 21st, 2017

    you r the best SHAH

  16. SHAH indian
    February 23rd, 2017

    Thanks

  17. Neil
    February 27th, 2017

    I had this in the ICND2, R3 router-ID configured on R6 AND a CHAP configuration mismatch (only configured on R6) I went with R3 router-ID as the issue.

  18. kala
    March 29th, 2017

    Any one please help me 545 q and 182 q is still valid or not .i want to give exam on 31 march?

  19. Dino
    March 29th, 2017

    Thank u so much SHAH!!!

  20. lucky
    March 30th, 2017

    if any wrote ccna exam means,please tell what are syllabus in ccna ,and what are the topics they added extra,if dumps are avaliable or not ? and plz forward that dumps,how much fees they are charging for the ccna exam,here the email is not allowing,if dumps are there means how you will
    forward,
    plz answer all above questions ?
    plz plz,plz,plz———————————————-
    thankyou

  21. kala
    March 30th, 2017

    325 us dollars fees

  22. Master
    March 31st, 2017

    hello do we need to configure or only use show commands to answer?

  23. Ghouri
    April 1st, 2017

    Hi, will some one send me the packet tracer lab of the above ospf lab?
    My email is {email not allowed}

  24. Anonymous
    April 3rd, 2017

    i have cleared CCNA 200-125 on 24-March-17….. 182 questions dump is not valid anymore.. I got lucky that I obtained 848 marks, but my friend fails to clear the exam using 182 question dumps..
    i got two labs..1 ACL and another OSPF
    rest 62 questions were very difficult.
    prepare theory properly this is the only way you can clear the exam.. “For Now”
    Best of Luck..

  25. Asad
    April 5th, 2017

    Need latest dumps for exam please shear at mention below email and anyone take the exam recently tell me whats in it … labs specially …
    Email : asadsumm022 @ gmail . com

  26. Dhisu
    April 9th, 2017

    Please send me the latest dumps @ karthika.dhisu @ gmail .com

    Thanks a lot.

  27. asap
    April 9th, 2017

    hi guys, I will be taking the exam this april 12 and I would like to ask if you have the latest dumps. please send send me the latest dump @

    {email not allowed}

    thank you very much!

  28. asap
    April 9th, 2017

    hi guys, I will be taking the exam this april 12 and I would like to ask if you have the latest dumps. please send send me the latest dump

    dmelqc @ gmail . com

    thank you very much!

  29. abby
    April 10th, 2017

    Anyone can post link to free pdf book for CCNA new exam format

  30. kk
    April 10th, 2017

    plz send me latest dumps of ccna exam on my mail-id

    plz plz {email not allowed}

  31. Bill Gates
    April 13th, 2017

    ospf routers dont show please add to SIM!! so we can add comands

  32. Ra
    April 13th, 2017

    hi ppl
    in ospf only show command or config too?

  33. Maz
    April 17th, 2017

    Is this OSPF SIM still valid for the latest exam? I’m giving my exam later this week.

  34. Anonymous
    April 19th, 2017

    Please can some one send me the latest dump for ccna 200-125 .
    i am planning to write my exam next week
    josifaz474 at yahoo * com

  35. nic
    April 19th, 2017

    man ready this material, i took the exm today, i sow a lot of question from here.

  36. Nitsss
    April 22nd, 2017

    Is this sim questions are still valid?

Comment pages
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