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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 (21) Comments
Comment pages
1 19 20 21 2243
  1. q 229
    July 31st, 2017

    a,b,f

  2. ZA
    July 31st, 2017

    @9tut, and to all, where can i see the question and answers for all sim’s as here i can see only explanation is given..

  3. Anonymous
    August 9th, 2017

    Thank you 9tut

  4. amaayra
    August 15th, 2017

    where is the link for zip file ??

  5. VK
    August 26th, 2017

    Hi Please send me latest ccna v3 dumps to zzntathi at gmail dotcom

  6. VK
    August 28th, 2017

    Hi Please send me the latest ccnav3 to zzntathi at gmail dotcom

  7. Ismail Ivan
    August 28th, 2017

    yah truly am not seeing questions for the sims
    i expected to see questions like
    routers does not form adjacencies with neighbors, or neighbor relationships what could be the problem…
    or just questions about the sims

    otherwise thanks @9tut
    i read one of icnd1 & 2 questions and answers..
    its very nice,well explained than even dumps from cisco itself
    if u dont know any thing, by reading icnd1 &2 from 9tut, u understand better and they stick forever

  8. osman
    August 31st, 2017

    can anyone please share the questions for these Sims. Please

  9. Engr. Jannel
    September 6th, 2017

    How to answer this OSPF lab question? through using show command?
    pls. answer pls. im going to take my ccna on sept. 9thank you

  10. Engr. Jannel
    September 6th, 2017

    asap… if you are all not busy

  11. hey folks
    September 6th, 2017

    can any one give me the latest dump

  12. Tufael
    September 7th, 2017

    Hello everyone, can someone share the latest dump for 200-125. Next week I will sit for the exam. Thank you so much!
    tufaelhossain @ gmail.com

  13. lino
    September 8th, 2017

    Hello everyone, can someone share the latest dump for 200-125. Next week I will sit for the exam. Thank you so much! gastonitiema74 @gmail.com

  14. Mercy
    September 22nd, 2017

    The program appears to be cogent and notice-grabbing. Rewarding Luck! I’ll be sitting down down in of…

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  15. Azif
    September 26th, 2017

    abyone send me ipv6 ospf simulation in pkt tracer ? azif_anjum(at the rate)hotmail.com

  16. Marian
    October 1st, 2017

    Hi,

    anyone has a .pkt file for this lab? Thanks for sharing!

  17. TechSavyAdventure
    October 29th, 2017

    Hello everyone, can someone share the latest dump for CCNA 200-125 as of 10/29/2017. 11/13/2017 I will be taking the test. Studied like crazy, from subnetting to simulations from the CCNA course I took. However, I have questions about some of the Simulation 9tut simulation questions (Ex: OSPF Neighbor Simulation-what are the questions?). What simulations are candidates running into lately. How many do you find on the test? I’ve studied all the 9tut simulations, but I hate to get caught off guard. Your help would mean a lot. A new job is waiting, and it would sure help to pass this for the sake of my family. Nervous I guess. Well, Thank you.

  18. TechSavyAdventure
    October 29th, 2017

    Please contact {email not allowed} for the latest CCNA 200-125 dump and advice. Please read above. Again, Thank you.

  19. shahid
    October 30th, 2017

    hi mr lou if u have lab sim of ospf then please up load

  20. Muhammad Siddique
    November 3rd, 2017

    Hi All
    Any one can help me with ICND2 valid Dumps , i am taking exam on 29 nov . iata2010uftaa(@)gmail.com

  21. Anton
    November 21st, 2017
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