OSPF Virtual Link and Summarization

18 Comments

1. when i try to add this topology in latest GNS3 it won’t load and give error 203 bad number of parameter pls fix it for all labs

2. Hi Praveen,

   Did you see our forum? Some other people had trouble with this. Did you fix it?

   Rene

3. Richard Bowman

   I had the same problem when I used the uncompressed ios.image file. I switched to the compressed ios.bin file and it loaded fine. Troubleshooting is all great fun.

4. I just spent 1 hour trying to configure the summerization [b]NOT[/b] from router dewey !! i thought the question said [b]NOT[/b] allowed , but it was totally worth it 🙂
   try it 😉

5. hehe well at least you learned a valuable lesson there! ;D

6. Hi, if you want more challenge configure MD5 authentication for Virtual link in addition. Not big task but good to know.

7. The virtual link addresses are different in the video and in the final configs. In the video it’s between 1.1.1.1 and 192.168.12.2, in the final configs it’s between 1.1.1.1 and 192.168.23.2.

   I “passed” this lab using the second solution (I didn’t peak, I swear :)), then I changed the virtual links when I verified my work by watching the video, and received this error:
   [quote]&#xOS;PF-4-ERRRCV: Received invalid packet: mismatch area ID, from backbone area must be virtual-link but not found from 192.168.12.2, FastEthernet0/0[/quote]

8. Hello Andras,

   It depends on the router ID of your OSPF router. OSPF will create a router ID by looking at the highest IP address on a loopback interface. If you don’t have a loopback interface it will use the highest IP address on an active interface. Router ID is not preemptive which means it will keep the same router ID unless you reset the OSPF process.

   If you configure a Virtual Link you need to configure it between the OSPF ROUTER ID. Not the IP addresses on the interface. That’s why it might be different for my or your config. I think I uploaded the final configuration at another day then recording the video which is why the router ID might be different.

   Good luck!

   Rene

9. I tried to advertise those loopback addresses via the redistribute connected subnets command in router Louise but for some reason router Huey will not receive the summarized /22 network. You need to specifically advertize the loopbacks via the network command for the summarization to work!! Interesting

10. Dewey will only generate a summary(the /22) if there is at least one of the subordinate routes in the routing table.
    It should not matter in any way what you did on Louie. You just need to advertise those loopbacks in area 2 and do the sumarization on Dewey then.

11. OSPF can be fun to play with 🙂 Keep in mind what Alexandru said, you need at least one route in your routing table in order for OSPF to advertise the summary. This applies to all routing protocols.

12. I had the same problem as IP5, misunderstanding the question! Spent the last 30 mins trying to figure out why summarization does not occur when running the area 2 range 172.16.0.0 255.255.252.0 on R3 (Louie).

13. This lab was amazing for me increase my summarization skills 🙂

    First, I tried redistribute the connected loopbacks from Louie to Dewey and enabled [b]area 2 range 172.16.0.0 255.255.252.0 [/b]command on Dewey, but it not worked.

    So we have two options for summarization:

    1 – Advertise all Louie loopback interfaces with [b]network[/b] and create the summary with [b]area 1 range 172.16.0.0 255.255.252.0[/b] command in Dewey, since this router is an ABR

    2 – Redistribute all Louie loopback interfaces with [b]redistribute connected subnets[/b] command and summary these address in Louie with command [b]summary-address 172.16.0.0 255.255.252.0[/b], since with [b]redistribute connected subnets[/b] Louie can be considered an ASBR. 🙂

14. Hi RENE ! so far i have learnt a lot from you . You are my virtual teacher 🙂

    This lab works fine but my question is ” What if we add another router attached with LOUIE and configure Area 3 on that , so how can we give a Virtual Link to that Area” ?

    I hope You could understand what i am asking 😉

    1. That sort of design with virtual-links is not supported. You could use tunneling as a method of extending area 0 across the network, assuming you already had IP connectivity between sites. So, an area 0 tunnel (GRE or IP in IP, as an example) between Huey and Louie would probably work. This is very poor network design, of course, as every single router is now an ABR and the benefit of using areas to segment an OSPF domain is lost.

15. Excellent. Spent about 30 minutes but eventually Victory!!

16. hey i didnt find .net file. Can anyone help me

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