# Subnetting Question

Registered Users Posts: 4 ■□□□□□□□□□
How many subnets and hosts per subnet can you get from the network 174.20.0.0/23 Remember for host part at least 2 bits are required?
Solve this question please and tell me the complete method ...

• Member Posts: 200
there are 128 subnets and 510 hosts from that network.

to get number of hosts
from /23 it means that 23 bits are on while others are off. so take number of bits which are off.
for there are 9 bits which are off
then 2^9 -2 =510 number of hosts.
for number of subnets
since it class B its default is /16.but according to the question is /23.
take 23-16=7
hence to get subnets =2^7 =128
• Member Posts: 41 ■■■□□□□□□□
Fadhil, I like you method.. How do you get the bits off?
• Member Posts: 828
its a 32 bit address with 23 (/23) bits for the network leaving 9 bits for the host.
The mask would be written in binary like this:
11111111.11111111.11111110.00000000
Ones being "on" and the zeros being the "off" bits.
• Member Posts: 374 ■■■□□□□□□□
yeah bro that method is smoking fast... bookmarking this now.
Goals for 2015: CCNP
• Member Posts: 200
thanks so much Union122 and geoffrey.a.davenport
• Member Posts: 76 ■■□□□□□□□□
The answer is: 510 hosts per subnet and 128 subnets.

11111111.11111111.11111110.00000000

Determine the hosts:
Formula: (2^h)-2=
(2^9)-2=510
Note: count the zeros for the hosts (h)

Determine the subnet:
Formula: 2^s=
(2^7)=128
Note: count the ones in the third octet.
• Registered Users Posts: 1 ■□□□□□□□□□
Good Day to All...!!!!

What will we say about the class of this IP

174.20.0.0/23

Either it is a Class B IP or example of Class less IP...

• Registered Users Posts: 4 ■□□□□□□□□□
thanks to all for this help .
• Member Posts: 200
Good Day to All...!!!!

What will we say about the class of this IP

174.20.0.0/23

Either it is a Class B IP or example of Class less IP...

that is class B ip address since class B range from 128 to 191 and class C range from 192 to 223
• Member Posts: 1,614 ■■■■□□□□□□
great help in this thread! thanks!
• Member Posts: 131
that is class B ip address since class B range from 128 to 191 and class C range from 192 to 223

I think this is considered a CIDR address (classless) because the default subnet mask of 255.255.0.0 for class B is not being used.
• Member Posts: 2,338 ■■■■■■■■□□
How many subnets and hosts per subnet can you get from the network 174.20.0.0/23 Remember for host part at least 2 bits are required?
Solve this question please and tell me the complete method ...

A /24 has 256 addresses. A /23 must has one bit more (twice as many addresses), and 256x2 = 512.
You generally subtract the all-zeroes and all-ones host addresses, leaving 510 host addresses.

174.20.x.x is Class B (16 network bits), so there are 23-16=7 subnet bits.
2^7 = 128 subnets total.
• Member Posts: 2,338 ■■■■■■■■□□
KenC wrote: »
I think this is considered a CIDR address (classless) because the default subnet mask of 255.255.0.0 for class B is not being used.
Subnetting predates and does not require CIDR. In this case, there are 16 network bits, 7 subnet bits, and 9 host bits. In fact, answering "How many subnets?" with a concrete number--as is typical--obligated us to make the classful assumption that there are 16 network bits!
• Member Posts: 131