subnet mask quick question

KarimbruxellesKarimbruxelles Posts: 7Users Awaiting Email Confirmation ■□□□□□□□□□
Hi Guys,

On Class C adress, borowing 3 bits for the subnet mask e.g 255.255.255.224
Can I assign host address starting from 1,2,3 etc... or shall I start to assign adress from 32?

e.g

200.1.1.2
255.255.255.224

OR

I can only start from

200.1.1.33
255.255.255.224


Please help as now I'm really confus


Thanks icon_redface.gif

Comments

  • EdTheLadEdTheLad Posts: 2,112Member ■■■■□□□□□□
    Hi Guys,

    On Class C adress, borowing 3 bits for the subnet mask e.g 255.255.255.224
    Can I assign host address starting from 1,2,3 etc... or shall I start to assign adress from 32?

    e.g

    200.1.1.2
    255.255.255.224

    OR

    I can only start from

    200.1.1.33
    255.255.255.224


    Please help as now I'm really confus


    Thanks icon_redface.gif

    This all depends if IP Subnet-Zero is enabled on your cisco router or not.
    In early releases on cisco IOS subnet-zero was switched off by default meaning the first and the last subnet were not used.
    So your above answer 200.1.1.33 255.255.255.224 would be correct.
    Now cisco enables subnet-zero by default which means the first and last subnet are counted so your above answer 200.1.1.1 255.255.255.224 would be correct.
    In the exam do not include subnet-zero if you are not explicitly told it is enabled.Now with reference to other ip vendor equipment like Riverstone,Alcatel,Redback blah blah blah they dont have the concept of subnet-zero and recognise all subnets by default.
    Hope this helps,but if you read the forum you will see this has been discussed before!!!
    Networking, sometimes i love it, mostly i hate it.Its all about the $$$$
  • KarimbruxellesKarimbruxelles Posts: 7Users Awaiting Email Confirmation ■□□□□□□□□□
    Thanks a lot for your quick answer

    Cheers

    Karimbruxelles
  • KarimbruxellesKarimbruxelles Posts: 7Users Awaiting Email Confirmation ■□□□□□□□□□
    But My 1st Hosts adress should start at 33 or ?
    e.g 200.1.1.33 255.255.255.224

    subnet number 200.1.1.32

    Because if I use 200.1.1.3 255.255.255.224 for e.g
    My subnet number will be 200.1.1.0

    Could you please clarify this?

    Thanks a lot
  • EdTheLadEdTheLad Posts: 2,112Member ■■■■□□□□□□
    with subnet-zero
    subnets= 0,32,64,96......224
    I think you should be able to work out the hosts?
    If not read a book

    without subnet-zero
    subnets=32,64,96......192
    I think you should be able to work out the hosts?
    If not read a book
    Networking, sometimes i love it, mostly i hate it.Its all about the $$$$
  • KarimbruxellesKarimbruxelles Posts: 7Users Awaiting Email Confirmation ■□□□□□□□□□
    OK I understand now :D

    I'm so glad, thx matte
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