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  1. Hey Rene Thanks for getting back. Sorry I did not frame my question correctly. I will try again ^_^.

    So I was trying to make topology diagram using the OSPF LSDB. I was not able to get the subnet mask for link R1 <–> R5. Then I went through the blog again and found this

    “R1 also has two stub networks, one to represent each of the point-to-point links shown above. Without these entries, other routers would not have routing information for the 10.0.15.0/24 and 10.0.12.0/24 subnets.”

    That’s what I was missing. I misunderstood the following LSA information with STUB as different loopback interface…

     Link connected to: a Stub Network
    (Link ID) Network/subnet number: 10.0.15.0
    (Link Data) Network Mask: 255.255.255.0
    

    But your blog clearly says that it is for sharing routing information. I should have read that before.
    Thanks for your efforts!

  2. Hello Rene,

    I have three questions:

    1. Can you please explain what vertex means? maybe an example will help me understand the concept.

    2. When you start analyzing R2 and it LSDB, how you determine that R2 has two networks with the same subnet. I can see R1-R2 subnet is 10.0.12.0/24 and LAN R2 is 10.12.0/24, as well.

    I got confused in this part:

    Link connected to: a Stub Network
    (Link ID) Network/subnet number: 10.0.12.0
    (Link Data) Network Mask: 255.255.255.0
    Number of TOS metrics: 0
    TOS 0 Metrics: 10

    I think the above entry in 2.2.2.2 is referring to the R1-R2 edge.

    1. Same thing, when you are describing the LSDB Optimizations:

    Under R3#show ip ospf database router self-originate, why you count 6 links, when 10.0.35.0/24 is the P2P between R3 - R5, but in the diagram you show as another link?

    Thanks,

    Jose

  3. Mark,
    Since LSA Type-2s are only associated with DRs, your statement is correct for networks where a DR has been elected (network type Broadcast, for example). In other network types (Point-to-Point, for example), it would be LSA Type 1.

  4. Hello Chaminda

    You are correct. The output should actually read:

    Link connected to: a Stub Network
     (Link ID) Network/subnet number: 10.0.35.0
     (Link Data) Network Mask: 255.255.255.0
      Number of TOS metrics: 0
       TOS 0 Metrics: 17
    

    where the (Link ID) Network/subnet number should be 10.0.35.0 and not 10.0.15.0.

    I will let Rene know to change that.

    The /24 in the label of that DR just indicates that this DR is performing its function for a point to point link, that is, a single /24 subnet. This is stated later on in the lesson as shown:

    image

    I hope this has been helpful!

    Laz

  5. Thank you for the explanation , Laz

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