How to advertise subnet into OSPF without network or redistribution command

During my CCIE R&S preparation for lab exam, I encounter a task that requested me to advertise a subnet into OSPF routing protocol, but without using network statement or redistribution command. Since back then I was a little confuse about this, I said to post here maybe it help others.

Please download the topology used in this example here. We have already OSPF prepared and the task request to advertise interface Loopack0 from R0 to OSPF without using network statement or redistribution command.

See how to do it here:

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Calin

Calin is a network engineer, with more than 15 years of experience in designing, installing, troubleshooting, and maintaining large enterprise WAN and LAN networks.

5 thoughts on “How to advertise subnet into OSPF without network or redistribution command”

  1. Hi Calin,

    Nice post! I was just wondering how about we use the interface command:

    int lo0
    ip ospf 1 area 0

    This should also meet the requirement of the lab, don't you think so?

    – James.

  2. Hi calin,

    Nice try, but still it's not working for me. I did the same configuration as u said, but still i cant ping 2.2.2.2 from 1.1.1.1 and loopbacks are not even getting advertised in the routing table on the opposite side…. It is still needed to give network command to advertise loopbacks.

    Give me solution.

    Thanks,
    Azhar

    1. Hello Azhar and thanks for visiting my page!

      Can you copy / paste here the OSPF / Loopback configuration?

      Also check the following:
      #show ip route -> check if the 1.1.1.1 and 2.2.2.2 are on the routing tables on the opposite routers
      #show ip ospf database -> if not in the routing table, check if the networks are in the OSPF database

      Best would be that you show here some config and then I can help you.

      Good luck!

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