Quick Subnetting Question

NetstudentNetstudent Member Posts: 1,693 ■■■□□□□□□□
I'm going through the questions on www.subnettingquestions.com

They have :

Question: How many subnets and hosts can you get from the network

Answer: 256 subnets and 254 hosts

I understand that they are using classfull subnetting, so I guess my question is how am I supposed to know when to use classfull subnetting and when to use classless? Will the question mention CIDR? If the question reads:

How many subnets and hosts can you get from the CIDR block

Would the answer be the same?
There is no place like BUT is my away from!


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    kafifi13kafifi13 Member Posts: 259
    I ran into the same problem. ON the exam will it tell you to subnet using classless?
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    ignign0ktignign0kt Member Posts: 42 ■■□□□□□□□□
    The network is classful if it uses a default network mask. /8 for class A, /16 for class B, and /24 for class C. Anything else is going to be classless and therefore using CIDR
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    malcyboodmalcybood Member Posts: 900 ■■■□□□□□□□
    Following on from what ignidn0kt said, if the specified address combined with subnet mask, is anything other than the below default values then you are using a classless address. Being able to determine that the address is classless, knowing host ranges of subnets, network and broadcast addresses is part of the exam objectives.

    Class A
    Address Range = -
    CIDR = /8
    Default Subnet Mask -

    Class B
    Address Range = -
    CIDR = /16
    Default Subnet Mask -

    Class C -
    CIDR = /24
    Default Subnet Mask -

    Once you learn subnetting properly you will be able to tell if an address is classful by combining network address & subnet mask.

    For example a network address of with subnet mask of is a classful class C address as the first octet is 199 (falls inbetween 192 - 223). The network address here would be and the broadcast leaving .1 - .254 as usable hosts.

    The same network address of with a subnet mask of is classless as you have used a /30 or .252 CIDR block. The network address would be and the broadcast would be leaving .1 and .2 as usable hosts
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