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  • supernetting/summarization

    A company got machine address from ISP and the n/w admin created 2 subnets,as and ,and assigned addresses from these ranges to all machines and devices , as the problem the client/company may face other packests (, ... so on) may send to the company's network... which creates loop problems...
    I want to make sumerization of of all these networks...
    to prevent the loop may occur ...
    '''May these possible ? having summarize address
    ,,,, ...
    how will be done?
    Need your guidance - Please

  • #2
    Re: supernetting/summarization

    I assume this is homework of some sort as we are talking about private ip ranges being accessible from the outside.

    If Company A purchased a class C block of addresses and they only use and then all traffic destined to any other network will be dropped at the edge router or firewall. There is no looping. Since that /16 block is assigned to them then yes (if these where public ip addresses) it will be routed to their edge and subsequently dropped (by ACL's etc) . Why would you except traffic for networks you do not route for or advertise? You could allow all traffic inbound from the outside for that range but if you are not routing or advertising those prefixes again they will just be blackholed. Summarization would depend on what networks you are including in the summary.

    ip summary address eigrp 1 would summarize these networks:

    (2 bits left over) = 4 exact matches seen below
    CCNA, CCNA-Security, CCNP
    CCIE Security (In Progress)


    • #3
      Re: supernetting/summarization

      1. An ISP wouldn't assign RFC 1918 addresses to a customer and they certainly wouldn't route traffic for those addresses.

      2. You wouldn't create a route summarization for the other networks, you would create a route summarization for your networks.

      3. The smallest route summarization (as far as I can figure) is, which would include networks:,,, and

      4. Regardless of the subnetting or route summarization that occurs, no "looping" exists. It's not clear to me what you mean with your loop statements.


      • #4
        Re: supernetting/summarization

        You can summarize routes for prefixes that are not in your routing domain such as a company partnership or merger etc. Peering with an ISP (BGP,OSPF etc)

        You would do this at the network edge as internal routers dont need routes for explicit prefixes since that edge router is the only path to those external prefixes. You could summarize said routes to your internal peers.

        The routing protocol used will determine where summarization can occur.

        Not sure what the "looping" is all about still.
        Last edited by auglan; 21st February 2012, 18:43.
        CCNA, CCNA-Security, CCNP
        CCIE Security (In Progress)