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Forum Replies

  1. That would be a good idea. I’ll write something soon.

  2. Great explanation Rene! I would be reading more IE stuff from your site!

    Please keep the writing on.

  3. Hi Kelvin,

    It’s a good question, most beginners ask me the same question. The “network” command for OSPF or EIGRP does two things:

    - It advertises the network.
    - It will start sending hello packets on the interface.

    So for this example, “network 172.16.1.0” and “network 172.16.3.0” are required because we want to advertise these networks.

    And “network 192.168.13.0” is required so that the two routers will send hello packets to each other through the tunnel, we need this so they can become neighbors.

    Does that make sense?

    Rene

  4. Hi Adrian,

    Once the GRE tunnel is up, it acts like a regular interface. With normal interfaces we also don’t see the next hop IP address within the IP packet.

    Here’s the logic of the router:

    1. When HQ sends a packet with destination 172.16.3.3 it has to check its routing table for a match:
    HQ#show ip route eigrp 
    
          172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks
    D        172.16.3.0/24 [90/27008000] via 192.168.13.3, 00:00:07, Tunnel1
    
    1. Above you can see that the next hop is the remote IP address of the tunnel. Now it has to do another lookup to fig
    ... Continue reading in our forum

  5. Hi Vitaly,

    The loopbacks won’t affect your neighbor adjacency whatsoever. The neighbor adjacency is established on the tunnel interface so any other interfaces don’t have any effect on it. It won’t matter if you use a /24 or /32 on the loopback interfaces :slight_smile:

    Do you still have your config with the /24s on the loopback that is not working?

    Rene

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