Finding subnet 300

[josephtbr]

Hello everyone i am a student and need help with a question

Assume a network topology has a network address of 99.0.0.0.

if 11 bits are used as a subnet bits hence subnet mask would be 255.255.224.0

Question asks to calculate the subnet address for Subnet 200 and Subnet 300?

Subnet 200 would be 

99.1100 1000.0000 0000. 0000 0000

= 99.200.0.0

how do i calculate the subnet address for subnet 300 if it has more than 255 bits?

[josephtbr]

I may be wrong in my subnet 200 workings though but if

subnet 1 is 99. 0000 0000. 0000 0000. 0000 0000

subnet 2: 99. 0000 0000. 0010 0000. 0000 0000

subnet 3: 99. 0000 0000. 0100 0000. 0000 0000

subnet 4: 99. 0000 0000. 0110 0000. 0000 0000

can i safely say that subnet 200 would be

subnet 200: 99.1100 1000.0000 0000. 0000 0000

or could it be just a name and a random subnet that falls between 

99. 0000 0000. 0000 0000. 0000 0000 and 99. 1111 1111. 1110 0000.0000 0000

[Harold Ritter · Accepted solution]

Hi @josephtbr ,

subnet 200 would be

200 = 0xc8 = 000 1100 1000 (expressed on 11 bits with leading zeroes, not trailing zeroes)

99.0001 1001.0000 0000.0000 0000 = 99.25.0.0/19

subnet 300 would be

300 = 0x12c = 001 0010 1100 (expressed on 11 bits with leading zeroes, not trailing zeroes)

99.0010 0101.1000 0000.0000 0000 = 99.37.128.0/19

Regards,

[josephtbr]

I see. Thank you very much.

[Harold Ritter]

You are very welcome @josephtbr and thanks for the feedback

[Harold Ritter]

One more thing @josephtbr ,

The above calculation assumes the first subnet is subnet 0, not subnet 1. Otherwise, you would need to subtract 1 from 200 and 300 before performing the suggested calculation.

The devil is in the details

Regards,

[josephtbr]

thanks. can the above calculation be used to find host bits as well lets say for pc 200 in subnet 200

i take 200 -2  which would give me  1100 0110

hence ip address for pc 200 would be

PC 200 = 99.0001 1001.0000 0000.1100 0110

= 99.25.0.198 /19

while

PC 1 = 99.0001 1001.0000 0000.0000 0001

PC 2 = 99.0001 1001.0000 0000.0000 0010

[Joseph W. Doherty]

No, basically remember 200 decimal = 1100 1000 binary.  Whether using such a value for a subnet or a host number, you (right) align it, within the IPv4 address bits allocated for it (host or subnet), and add leading zeros, if needed.  Host values are always aligned with the right most bit.

To possibly further clarify what @Harold Ritter mentioned about whether you need to allow for one, the first host number or first subnet number is zero, the second host/subnet number is 1.  To further confuse things, in IPv4, the first host address for /30 and larger is host number 1 (this because for /30s are larger, the first host number, zero, is set aside for just network prefix).

In some situation, you can bump into issues using subnet number zero, too.

Also, BTW, subnets (and supernet), are really part of Classful addressing, but under classless (IPv4) addressing, you just have a network number and a host number.

[josephtbr]

Thanks for clarifying. That is why in my calculation for the host address I subtracted 2 from 200 for the network prefix and the broadcast address before converting it to binary.

[Joseph W. Doherty]

You wouldn't do that for subnet numbering.  For subnet 200 you use 200.  For the 200th subnet, you use 199, the latter because, as noted earlier by @Harold Ritter, subnet numbering starts with zero.

[MHM Cisco World]

dont waste your time there is online subnet calculator

 the accept value is 255.255.254.0 which give you 512.

[MHM Cisco World]

the /19 give 8192 host IP not give 300.
again use online calculator 
the worlds start to use chatGPT  so we must go ahead using tech. 
use fast way dont waste your time in these issue. 

[Joseph W. Doherty]

I believe you misunderstand OP's question, which wants subnet 300 not a subnet that can support 300 hosts.

[MHM Cisco World]

the subnet max is 255 there is no subnet 300, 
so his Q is already wrong 

[Joseph W. Doherty]

Subnet 300 is valid because he started with a Class A.  Also valid for a Class B.  Invalid for Class C.