Notable Replies

  1. Rene,

    I have a doubt, all examples that you gave are "continuos" networks and an even number of networks.
    And when we have networks like below? I just can solve them with binary method. Is there another form?

    I choosed shortest and highest networks and convert them to binary, so the summary address will be a block size 64 networks. I can't solve it using CIDR notation and block size method.

    Another example with an odd number of networks, I can solve it with binary method / 24 / 24 / 24 / 24 / 24

    The summary address will be, but when I was writing this example I saw that if I use block
    size it's able solve it too. It's need always think in block size like "powers of 2".

    When you have a free time, please, detail below

    8 + 8 + 6 = 24 bits

    Hug and thanks for yours articles. It's helping a lot :slight_smile:

  2. Hey Rene,
    I was following you example but got confused on these: 10101100.00000001.00000100.00000000 10101100.00000001.10000000.00000000 10101100.00000001.00000101.00000000 10101100.00000001.00000110.00000000 10101100.00000001.00000111.00000000

    Particularly the 2nd one Following your example using the 3rd octet has a 128 in it, so how would I factor this in as the other octets are using the first 5 bits.


  3. Hi James,

    Where did you find this example? It's not on this page? :slight_smile:


  4. Hi Rene

    What are the disadvantages of using Route Summarization? Can you explain those with some examples pl.

  5. Hi Lokesh,

    There are a couple of potential issues.

    1) You can blackhole traffic. For example let's say you have these 4 networks behind a router: /24 /24 /24 /24

    If you would create a summary like /20 then basically you are advertising the - range to other routers. When your router receives a packet with destination or something it will drop it.

    2) Asymmetric routing, This one is harder to explain with text only. When you advertise a summary it's possible that other routers will select a different (more specific) path as the next hop.

    3) Traffic engineering: If you use a routing protocol then you can play with the different metrics for each prefix. If you advertise a summary instead of all the different prefixes then you won't be able to change metric (or BGP attributes) for a single prefix.


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