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help me how to subnet class A, B & C

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17 years 3 months ago #20823 by ashok_nitc
i think you need to discuss with your teacher once again! whatever statistics you have given is right but while desigining the network you can use 255.255.255.240 /28 as a subnet musk for your network(whether its class A,B or C).

everything depends upon your network..means number of subnet you requre and no of host per subnet is required and Class(A,B or C) you are using.


and i think you understood that 255.255.0.0 is not a class A ip address!!!
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17 years 3 months ago #20825 by Smurf
I'm with ashok_nitc on this one, no idea where you have got this from (but i am doing some research to see if i can find what you have read).

This is taken from the TCP/IP Guide;

Class A = First Octect IP Address is 00000001 to 01111110 - In Decimal first Octect 1 to 126 - Octects in Network ID/Host ID - 1 / 3 therefore this is 255.0.0.0
Class B = First Octect IP Address is 10000001 to 10111110 - In Decimal first Octect 128 to 191 - Octects in Network ID/Host ID - 2 / 2 therefore this is 255.255.0.0
Class C = First Octect IP Address is 11000001 to 11011110 - In Decimal first Octect 192 to 223 - Octects in Network ID/Host ID - 3 / 1 therefore this is 255.255.255.0
Class D/E Omitted

This applies if you want to stick to Classful addressing. Classless is then where you start to change the Subnet Mask to start looking at VLSM

Wayne Murphy
Firewall.cx Team Member
www.firewall.cx

Now working for a Security Company called Sec-1 Ltd in the UK, for any
Penetration Testing work visit www.sec-1.com or PM me for details.
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17 years 3 months ago #20828 by durk21
Replied by durk21 on topic hmmm?
for IP addresses it's 1 to 127 and so on

i.e

class A

1.0.0.0 to 127.0.0.0 IP address

255.128.0.0 is actually the first subnet though for a class A

for class B 128.0.0.0 to 191.255.255.255

255.255.128.0 is the first subnet

for class C 192.0.0.0 to 223.255.255.255

255.255.255.128 being the first subnet there

I'm not talking about TCP/IP I'm just talking about subnets and subnetting calculations
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17 years 3 months ago #20829 by durk21

and i think you understood that 255.255.0.0 is not a class A ip address!!!


I never said it was an IP address!! I said it fell under a CLASS A SUBNET! Which will be paired with a Class A IP address.

and to quote Smurf

his is taken from the TCP/IP Guide;

Class A = First Octect IP Address is 00000001 to 01111110 - In Decimal first Octect 1 to 126 - Octects in Network ID/Host ID - 1 / 3 therefore this is 255.0.0.0
Class B = First Octect IP Address is 10000001 to 10111110 - In Decimal first Octect 128 to 191 - Octects in Network ID/Host ID - 2 / 2 therefore this is 255.255.0.0
Class C = First Octect IP Address is 11000001 to 11011110 - In Decimal first Octect 192 to 223 - Octects in Network ID/Host ID - 3 / 1 therefore this is 255.255.255.0
Class D/E Omitted


you are correct but part of that is for IP address ranges not subnet ranges. It does also go 1/3 2/2 3/1 BUT if u paid attention that is how I have it in my chart
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17 years 3 months ago #20832 by Dove
Hiya,

while doing VLSM, no need to worry about the IP Class range. The class type is only belongs to the IP range which you are using...as you mentioned on earlier post and its not depends to subnetmask..... :wink:


The subnet mask is puerly used to define the number hosts, subet(networks), Network and Broadcast address for each subnets...for the given IP (what ever the class the IP belongs to)....


Dove
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17 years 3 months ago #20833 by durk21
CLASS A SUBNETS
255.128.0.0 / 9
255.192.0.0 / 10
255.224.0.0 / 11
255.240..0.0 / 12
255.248.0.0 / 13
255.252.0.0 / 14
255.254.0.0 / 15
255.255.0.0 / 16

Power of 0's
2^23 - 2
2^22 - 2
2^21 - 2
2^20 - 2
2^19 - 2
2^18 - 2
2^17 - 2
2^16 - 2

Power of 1's
2^1 - 2
2^2 - 2
2^3 - 2
2^4 - 2
2^5 - 2
2^6 - 2
2^7 - 2
2^8 - 2



Number Of Hosts
8,388,608
4,194,302
2,097,150
1,048,574
524,286
262,142
131070
65534

Number Of Subnets
0
2
6
14
30
62
126
254

IP ADDRESS RANGES
1 - 126
1.0.0.0 - 127.0.0.0
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