Summarizing an address

__bazzinga____bazzinga__ Registered Users Posts: 2 ■□□□□□□□□□
Can someone please help me with this:
Summarize the following without over-summarizing:
And how will the summarized address look if I add

My answer would be and the summarized address won't change if we add

Also I would like to know what is the difference between not over-summarizing and over-summarizing with these same addresses.


  • hurricane1091hurricane1091 Member Posts: 919 ■■■■□□□□□□
    Your answer is correct and nothing changes if you add that address. covers

    If you did, you would be over-summarizing because you are covering subnets that are not being asked to be summarized. It doesn't really apply here, but if you pretend that you were looking to include and, using would be over-summarizing because the summary includes additional address blocks that you are not necessarily trying to advertise in the summary address. To do it properly, you may consider two summary addresses; and You can go with in that hypothetical example I provided potentially, but I would recommend going with the two separate summaries. Hope that helps.
  • __bazzinga____bazzinga__ Registered Users Posts: 2 ■□□□□□□□□□
    If I want to be sure to not over-summarize can I make 2 summarized addresses, and, where would also include the added address?
    Also, thank you very much for answering.
  • p@r0tuXus[email protected] Member Posts: 532 ■■■■□□□□□□
    For address summarization, whether for your ACLs or your Route Statements, the VLSM for CCNA level studies will probably require one address, not two, and this is just to ensure you know how to summarize. It's probably best not to over-complicate the CCNA as it's all ready a lot to wrap your head around.

    For the listed addresses above, you would summarize the largest necessary address and mask and no more. /21

    Address / Mask- Binary Address (Network/Host Bits) 00001010.00010110.00000000.00000000 00001010.00010110.00000010.00000000 00001010.00010110.00000011.00000000 00001010.00010110.00000100.00000000 00001010.00010110.00000110.00000000 00001010.00010110.00000111.00000000 00001010.00010110.00000111.00000000

    The last octet is fairly irrelevant, the largest host bit number in the 3rd octet becomes the most relevant as you'll have to have enough network bits to accomodate in the subnet mask to encompass all the ranges. Hence: /21 would work fine.
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