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IPv6 OSPF Virtual Link Sim

May 8th, 2014 in Lab Sim, LabSim Go to comments


TUT is a small company that has an existing enterprise network that is running IPv6 OSPFv3. However, R4’s loopback address (FEC0:4:4) cannot be seen in R1. Identify and fix this fault, do not change the current area assignments. Your task is complete when R4’s loopback address (FEC0:4:4) can be seen in the routing table of R1.


Special Note: To gain the maximum number of points you must remove all incorrect or unneeded configuration statements related to this issue.

Answer and Explanation:

To troubleshoot the problem, first issue the show running-config on all of 4 routers. Pay more attention to the outputs of routers R2 and R3

The output of the “show running-config” command of R2:


The output of the “show running-config” command of R3:


We knew that all areas in an Open Shortest Path First (OSPF) autonomous system must be physically connected to the backbone area (Area 0). In some cases, where this is not possible,we can use a virtual link to connect to the backbone through a non-backbone area. The area through which you configure the virtual link is known as a transit area. In this case, the area 11 will become the transit area. Therefore, routers R2 and R3 must be configured with the area area-id virtual-link neighbor-router-id command.

+ Configure virtual link on R2 (from the first output above, we learned that the OSPF process ID of R2 is 1):

R2#configure terminal
R2(config)#ipv6 router ospf 1
R2(config-rtr)#area 11 virtual-link

(Notice that we have to use neighbor router-id, not R2’s router-id

+ Configure virtual link on R3 (from the second output above, we learned that the OSPF process ID of R3 is 1 and we have to disable the wrong configuration of “area 54 virtual-link”):

R3#configure terminal
R3(config)#ipv6 router ospf 1
R3(config-rtr)#no area 54 virtual-link
R3(config-rtr)#area 11 virtual-link

We should check the configuration on R4:

R4#show running-config

You will see a wrongly configured virtual-link command. To get full mark we have to disable this command:

R4#configure terminal
R4(config)#ipv6 router ospf 1
R4(config-rtr)#no area 54 virtual-link

After finishing the configuration don’t forget to ping between R1 and R4 to make sure they work well!

Now all the configuration was done. But we still cannot ping the IPv6 loopback interface of R4 from R1 because the IPv6 loopback interface of R4 has not been advertised into OSPFv3. But we can check by using the command show ipv6 route on R1. If you can see the IPv6 loopback interface of R4 then you don’t need to do anything else.

But in real routers, we have to advertise the IPv6 loopback interfaces of R1 & R4 into OSPFv3 to make them appear in the routing tables with the following commands:

R4(config)#int loopback 0
R4(config-if)#ipv6 ospf 1 area 54

R1(config)#int loopback 0
R1(config-if)#ipv6 ospf 1 area 0

Again, the above commands should only be used when you don’t see the IPv6 loopback interface of R4 in the IPv6 routing table of R1 as the exam requirement.

The copying running-config startup-config command will not work but don’t worry, just skip it.

Notice: If you issue the command “show running-config” on R1, you will see these two lines:

passive-interface default
no passive-interface fa0/0 (fa0/0 is the interface connecting with R2)

These two lines make all the interfaces of R1 become passive interfaces except interface fa0/0. They are correctly configured so don’t try to disable them.

Other lab-sims on this site:

EIGRP Stub Sim


EIGRP OSPF Redistribution Sim

EIGRP Simlet
Policy Based Routing Sim

Comment pages
1 2 3 32
  1. Shabooyma
    January 22nd, 2019

    Hello friends,
    can someone share the update dumps of CCNP RS 300-101

  2. SW
    January 22nd, 2019

    Hi Guys, Hope you are fine… Can you please assist me in order to get CCNP ROUTE dumps.


    Thanks in advance for the attention & consideration.

  3. Admiral
    January 22nd, 2019

    “It is weird that we can’t ping the IPv6 loopback interface of R4 (with the ping or ping ipv6 command) but we can check by using the command show ipv6 route on R1”

    Just assign an ipv6 address to the fa0/0 interface of R1 and ping will pass correctly.

  4. Anonymous
    January 25th, 2019

    Guys in the exam they did not ask to ping they just say:

    Your task is complete when R4’s loopback address (FEC0:4:4) can be seen in the routing table of R1.

  5. boomboom
    January 26th, 2019

    just a show ip route on R1 shall do it.

  6. Hagler
    February 14th, 2019

    Did anyone tried to do this one GNS3?
    Because in reality, at GNS3, if you remove area 54 virtual-link it will not perform adjacency and R3 will not learn R4 loopback (FEC0:4:4).

    Any thoughts? ill still go with what digitaltut and everybody here experienced but would like to know if anyone saw it and explain what happened


  7. Andrew
    February 17th, 2019

    Same thing happened to me,
    unable to find R4 Loopback ip in R1 after removing area 54 command
    did u found any solution for this

  8. Anonymous
    February 20th, 2019

    Don’t over-complicate it guys…it’s pretty damn easy.

  9. gent
    February 20th, 2019

    im not see R4’S Loopback on r1 after doing this

  10. juls
    February 21st, 2019

    I have the same problem, using GNS3 is neccesary to keep virtual-link between R3 and R4, not just between R2 ans R3.
    I created the link between R2 and R3 and R1 was not able to learn route to R4. After several attempts, I re add again link between R4 and R3 and Ping is succesful.

  11. Anonymous
    February 24th, 2019

    Hi guys,

    quick question, see when it comes to configuration for these sims, how is it done in the actual exam? Do we configure right onto a CLI or do we insert commands into boxes like on these SIMS ?

  12. Anonymous
    February 24th, 2019

    Hi Guys,

    Can someone please explain to me why we need a virtual link on R2, when that has an interface already connected to Area 0? Even the explanation above mentions that we use a virtual link to connect to Area 0 when the device cannot physically connect to the backbone area…

    Also, to reply to my buddy @Anonymous above, I believe we will be using CLI rather than the text boxes on digitaltut.

  13. k3n3
    February 25th, 2019

    guys on all the sims, do we need to wri mem or save the config or not? for as long as it will work?

  14. Antares
    March 8th, 2019

    If you are looking for latest dumps just email me antaresccnp @ outlook . com.

    I have also latest Switch and T-SHOOT.

  15. meloo
    April 1st, 2019

    Pass today, 925
    Chinese dump valid
    Labs PBR, EIGRP OSPF redistribute, IPv6

  16. meloo
    April 1st, 2019

    Thanks digitaltut and all!
    email: philipsmeloo @gmail .com

  17. joanale
    April 21st, 2019

    you need to use virtual link to connect external areas R1 with R4.

  18. Dotcom
    June 3rd, 2019

    Guys can some please share sites where we can find latest dump. someone who is not selling the dumps please.

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