Subnet Question

nuglobenuglobe Posts: 190Member
I have been reading two books in prep for the CCNA, I can seem to do most of the subnetting question except for these kind.

193.216.0.0
Mask = 255.255.248.0

How do I apply that mask to a class C ip? The third octet would be part of the network address. So I mean, unless I just use the last octet and have all bits for the host... but ... err... ahh

Could someone clear this up for me?
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Comments

  • mikej412mikej412 Posts: 10,090Member
    nuglobe wrote:
    I have been reading two books in prep for the CCNA, I can seem to do most of the subnetting question except for these kind.

    193.216.0.0
    Mask = 255.255.248.0

    How do I apply that mask to a class C ip? The third octet would be part of the network address. So I mean, unless I just use the last octet and have all bits for the host... but ... err... ahh
    Once you move away from classful addressing -- you're not in Kansas anymore Toto!

    If it were a Class B address you were starting with - like 172.216.0.0 would you be able to do it then?

    Since it would be a Class C address -- if you were classful -- that subnet mask means you are supernetting. Rather than taking one network range, and splitting it up into more networks of fewer hosts -- you are combining multiple contiguous networks into one network with a larger number of hosts.

    So.... 256-248 gives you ...... what?

    And your 2^n and 2^n-2 formulas still work (and once you go classless, you also usually go subnet zero).

    If you had an "ah-ha!" moment with subnetting, you should soon have an "oh" moment with supernetting.
    :mike: Cisco Certifications -- Collect the Entire Set!
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