OSPF network statement

Hi

In the lab exam, if "network 0.0.0.0 255.255.255.255 area 0" is pre-configured for us but in the diagram ospf is running on only on one interface of the router while other interfaces are also running some other routing protocol.

In order to accomplish some other task, can we change this network statement to the more specific ospf network statement ?  

Comments

  • In order to accomplish some other task, can we change this network statement to the more specific ospf network statement ?  

    What do you mean "to accomplish some other task"?

  • In order to accomplish some other task, can we change this network statement to the more specific ospf network statement ?  

    What do you mean "to accomplish some other task"?

    For example

    -----EIGRP-----(f0/1)R1(S0/0)------OSPPF---------

    R1 has "network 0.0.0.0 255.255.255.255 area 0" under ospf process. Eigrp is also running on R1's f0/0. Now we need to redistribute from eigrp into ospf. Since ospf is running on R1's f0/0 it can not be resistribute into ospf itself because its already running ospf and hence we wont have connectivity into the eigrp domain.

    In such cases are we allowed to change 0.0.0.0 network statement to more specific network statement. 

     

  • I think we are allowed to use every command we have in our ammo belt in the lab as long as we do not violate the "YOU ARE NOT ALLOWED TO DO..."-section that is written in the lab.

     

    Regards!

  • In order to accomplish some other task, can we change this network statement to the more specific ospf network statement ?  

    What do you mean "to accomplish some other task"?

    For example

    -----EIGRP-----(f0/1)R1(S0/0)------OSPPF---------

    R1 has "network 0.0.0.0 255.255.255.255 area 0" under ospf process. Eigrp is also running on R1's f0/0. Now we need to redistribute from eigrp into ospf. Since ospf is running on R1's f0/0 it can not be resistribute into ospf itself because its already running ospf and hence we wont have connectivity into the eigrp domain.

    In such cases are we allowed to change 0.0.0.0 network statement to more specific network statement. 

     

     

    Hi dcancerian,

    Yes - in this case we are allowed to change it in order to accomplish the goal. But always refer to the lab's do's and don'ts

  • Technically while you keep older statement with you and put more specific statement like for example say S0/0 is 1.1.1.1/30, and you put " net 1.1.1.1 0.0.0.0 a 0", the more specific statement actually should take over. In older IOS the order might have been consideration like putting more speicific command first and less specific later, but shouldn't be a problem in newer versions.

    Try it...

     

    HTH...

    Deepak Arora

    http://deepakarora1984.blogspot.com

     

  • Technically while you keep older statement with you and put more specific statement like for example say S0/0 is 1.1.1.1/30, and you put " net 1.1.1.1 0.0.0.0 a 0", the more specific statement actually should take over. In older IOS the order might have been consideration like putting more speicific command first and less specific later, but shouldn't be a problem in newer versions.

    I understand that in new version of IOS more specific statement take over the less specific once but the case i presented earlier in this post if i configure more specif statement on S0/0 that will not solve any problem because we still have f0/1 which is running ospf and that i want to redistribute that into ospf to provide ospf domain reachability to eigrp domain.

  • R1 has "network 0.0.0.0 255.255.255.255 area 0" under ospf process. Eigrp is also running on R1's f0/0. Now we need to redistribute from eigrp into ospf. Since ospf is running on R1's f0/0 it can not be resistribute into ospf itself because its already running ospf and hence we wont have connectivity into the eigrp domain.

    In such cases are we allowed to change 0.0.0.0 network statement to more specific network statement. 

    Yes, in this case you must change the network statement to specific network.

  • I understand that in new version of IOS more specific statement take over the less specific once but the case i presented earlier in this post if i configure more specif statement on S0/0 that will not solve any problem because we still have f0/1 which is running ospf and that i want to redistribute that into ospf to provide ospf domain reachability to eigrp domain.

    I tried on 15.x version but got same result as 14.x. I couldn't see any result of repleacement more specific statement to less specific statement:

    See here:

    R6(config-router)#do show ip route
         4.0.0.0/32 is subnetted, 1 subnets
    O E2    4.4.4.4 [110/20] via 56.56.56.5, 00:07:55, FastEthernet0/0
         5.0.0.0/32 is subnetted, 1 subnets
    O       5.5.5.5 [110/2] via 56.56.56.5, 00:07:55, FastEthernet0/0
         6.0.0.0/32 is subnetted, 1 subnets
    C       6.6.6.6 is directly connected, Loopback0
         56.0.0.0/24 is subnetted, 1 subnets
    C       56.56.56.0 is directly connected, FastEthernet0/0
         45.0.0.0/24 is subnetted, 1 subnets
    O       45.45.45.0 [110/2] via 56.56.56.5, 00:07:55, FastEthernet0/0

    I have R4-EIGRP-R5-OSPF-R6 topology, I configured network 0.0.0.0 0.0.0.0 area 0 on R5. R6 getting 45.45.45.0 route as a internal OSPF route after redistribution also but 45.45.45.5 is purely configured to EIGRP. If more specific statement replce less specific statement, you should get as a external route on R6.

    So configure specific route to be safe and sure!!!

  • I have R4-EIGRP-R5-OSPF-R6 topology, I configured network 0.0.0.0 0.0.0.0 area 0 on R5. R6 getting 45.45.45.0 route as a internal OSPF route after redistribution also but 45.45.45.5 is purely configured to EIGRP. If more specific statement replce less specific statement, you should get as a external route on R6.

    This scenario is a part of large topology for which i wanted to have ospf external routes on R6. In that case we require to have moe specific statement at R5 otherwise we will only have internal ospf routes at R6.

    Actually my question was not to debate this behaviour but to ask whether we are allowed to change preconfigured less specific network statement to more specific statement in the lab exam.

  • Correct dcancerian. In such a situation in the lab, you should be allowed to change this to a more specific network statement.

    HTH

  • Correct dcancerian. In such a situation in the lab, you should be allowed to change this to a more specific network statement.

    You are probably right but still have not got confirmative answer, anyways we always have proctor in the lab exam for such queries.

  • Also - remember the passive-interface command to disable hello/lsa on interface. This will still advertise the interface in OSPF, but will not form adjacencies.

    Between modifying existing configuration or adding the passive-interface command, you should be able to meet the requirements. If there is a doubt, present the alternatives to the proctor, showing that you understand the effect each option will have.

    Correct dcancerian. In such a situation in the lab, you should be allowed to change this to a more specific network statement.

    You are probably right but still have not got confirmative answer, anyways we always have proctor in the lab exam for such queries.


  • I'm not sure i understand your problem. You can run as many different protocols on any interface as you like.

    If you run OSPF you can run EIGRP as well. So you can still redistribute.

    If you ran OSPF on both interfaces there would be no need to redistribute.

    If you ran 2 different OSPF processes then i suppose you could redistribute on R1.

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