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Forum Replies

  1. Hi Lokesh,

    Let’s say you have these routes:

    192.168.0.0/24 - cost 10
    192.168.1.0/24 - cost 20
    192.168.2.0/24 - cost 5
    192.168.3.0/24 - cost 30

    When you create a summary route that matches these 4 routes then we will have to pick a cost. By default, it will use the lowest cost for the summary route…5 in this case.

    Rene

  2. Hi Jason,

    172.16.0.0 0.0.3.255 is an exact match for these four networks:

    • 172.16.0.0
    • 172.16.1.0
    • 172.16.2.0
    • 172.16.3.0

    You could have used the 0.0.0.255 wildcard but then you would require a network statement for each 172.16.x.0 network. Another option could be 172.16.0.0 0.0.255.255 but that means any interface in the 172.16.x.x range would be advertised.

    Rene

  3. Rohan,
    Yes. The only way to get networks into OSPF is either to redistribute them (from locally connections or from another routing protocol), or to explicitly add them to OSPF via a “network” statement. Since using the network state would not result in the routes being seen as external (the purpose of the exercise), there is no other option than redistribution of some form.

  4. Hello Sims,

    I tried a different example from the one which are shown in the lesson, just to make sure that I understand OSPF summarization well enough. But unfortunately, I couldn’t make it work. Can you please review and let me know what’s done wrong? Thank you for your support.

    R1-R3-R5 (Area 1)
    R1-R2 (Area 0 - Gbps link* and reference bandwidth has been adapted to all routers to 1000)
    R2-R4-R6 (Area 2 - but it’s not configured / used in this example)

    R1 f1/0 and g0/0 interfaces have “ip ospf priority 2” to make the R1 the DR for all the segments.
    R3 router-i

    ... Continue reading in our forum

  5. Hi @tsirgogik

    Which area range command did you use? On R1, this should work:

    router ospf 1
    area 0 range 10.10.8.0 255.255.248.0
    

    You can make your summary a bit more specific btw, 255.255.252.0 will cover 10.10.8.0/24 - 10.10.11.0/24

    Rene

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