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?

[MHM Cisco World]

you have 8 bits how you get 300 from 8 bits !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[Joseph W. Doherty]

Laugh, you don't (from 8 bits).

With a Class A you have 24 host bits, to take for subnetting.  16 host bits for a Class B.

OP describes taking 11 bits from a Class A's host bits, which, of course allows for subnets 200 or 300.

[MHM Cisco World]

Laugh please share the subnet 300, I need to see it IP and subnet mask

[Joseph W. Doherty]

"Laugh please share the subnet 300, I need to see it IP and subnet mask"

Hmm, that info was already provided:

@Harold Ritter :

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

@josephtbr 

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

Since I'm not adverse to using subnet calculators, maybe this will help too:

Notice, this subnet calculator has no issue with working with a Class A network with an 11 bit subnet.  It even notes 2,048 (2 ** 11) subnets are possible.  Unfortunately, this calculator, doesn't show the subnet as a discreet number, and I'm unaware of any that would (in my case, I've been using CIDR addressing for decades, so it don't "think" subnets).

[MHM Cisco World]

....

[Joseph W. Doherty]

Oh, too bad you deleted all your post's information - as you had a couple of good questions.

"so he ask 
99.300.x.x <<- how you get this ???"

OP didn't actually ask that, but certainly implied that because of thinking

"Subnet 200 would be 

99.1100 1000.0000 0000. 0000 0000

= 99.200.0.0"

which @Harold Ritter correctly described as being incorrect (for an 11 bit subnet - would be correct for an 8 bit subnet).

"99.37.128.0 <<- I sum all the subnet number to get 300 ??"

Correct, i.e.:

37*2³+128/2⁵=300

[MHM Cisco World]

this not acceptable from my side EVER 
subnet 300 can not get the bit is divide into 8 bits and max is 255. 
this my way to understand topic.

[MHM Cisco World]

this not acceptable from my side EVER 
subnet 300 can not get the bit is divide into 8 bits and max is 255. 
this my way to understand topic.

[Joseph W. Doherty]

"this not acceptable from my side EVER"

Well, I certainly won't force you to use subnet larger that 8 bits, but then again, I would recommend you not use Classful subnets at all.

"subnet 300 can not get the bit is divide into 8 bits and max is 255. 
this my way to understand topic."

Again, I fully agree you cannot have a subnet 300 with only an 8 bit subnet allocation.  (Oh, BTW, as you can often use subnet zero, if being used, with 8 bits you can have 256 subnets, not just 255.)

In this case, OP specified an 11 bit subnet allocation.  In fact, one of the "errors" in OP's understanding was, thinking 200 as the second octet value, would be subnet 200 using an 11 bit subnet allocation (incidentally, 99.200.0.0/19 would be subnet 1,600, I believe).  @Harold Ritter explained why 99.200.0.0 was not subnet 200 (for the /19).

As to how you understand the topic, then I would suggest you don't fully understand subnetting.  Possibly your networking experience doesn't go back far enough, like into the last century, when Classful subnetting was the "norm".  Another aspect of subnetting that often confused was dealing with "discontinuous" subnets.  Supernetting was also often misunderstood too.

[Joseph W. Doherty]

BTW, @MHM Cisco World, what do you believe the subnet value for 99.37.128.0/19 is (using Classful addressing)?

What would be the (Classful) subnet values for?:

99.37.130.0/19
1.128.1.1/9
1.128.2.2/10
1.128.64.64/15
1.128.128.128/16

[MHM Cisco World]

these two table select the correct one

we can not write the IP in decimal->binary convert directly we  must divide the bit into 8 bits, that why IP contain ""."" in-between you take each part convert it to binary 


and again his Q is wrong there is no thing called subnet 300.
and again dont waste your time with this calculation you need some acknowledge  to know the IP and it bit and use online calculator 

[Harold Ritter]

Hi @MHM Cisco World ,

> his Q is wrong there is no thing called subnet 300.

What the original poster refers to is the 200th and 300th subnets. Given that the basic network is 99.0.0.0/8 and that the subnet length is /19, it leads to 11 bits for subnetting (2^11 = 2048), therefore 2048 /19 subnets out of that 99.0.0.0/8.

These 2048 subnets will start with 99.0.0.0/19 (1st subnet) and runs through 99.255.224.0/19 (2048th subnet).

So it is a very legitimate question.

Regards,

[Joseph W. Doherty]

Like @Harold Ritter , @OP's assigned question was perfectly valid.

OP's "solution" for subnet 200 was incorrect and it lead to a specific question for how you do the same for subnet 300, as dotted decimal octet cannot exceed 255.  (Actually this assignment may have been intended to lead one down the, incorrect, path taken by the OP.  Learning by mistakes is not always a mistake.  [I'm hoping others will learn from Harold's and @MHM Cisco World other postings too.])

[Joseph W. Doherty]

I can see you're really struggling with the concept of subnet 300.  Let's try another question that I expect you'll have no problem with.

With CIDR addressing I ask you to provide me a private IPv4 network, from the 192.168.x.x address space, to support 300 hosts.  What might you suggest?

However, also explain how the network prefix you provide supports this as IPv4's dotted decimal notation's octets cannot exceed 255.

Bonus questions would be how would you answer the above, using Classful rules for both Class B and Class C addressing using subnetting and supernetting, respectively.

BTW, if you try to work out the subnets I asked about in my prior posting, that may also help you to understand how we can have a subnet 300.

[Joseph W. Doherty]

BTW, sorry, purpose of those tables is unclear, at least to me.

Also, BTW, I disagree about writing an IPv4 address, if you're saying it can only be written in dotted decimal.  I do agree its dotted decimal values each represent one octet, and as such, would be in the range of 0..255.

Again, you're struggling with the concept of a subnet 300 being possible.  Whoever posed the assignment to the OP implies it's possible.  @Harold Ritter (a CCIE) and I believe it's possible.  So, just for laughs, consider it really is possible, just you don't understand how it is possible (yet).  With such mindset, reread all our postings.  If still unclear, post a question on a point of confusion or unclarity.

Personally, if we were together in a room with a blackboard, I believe you would understand this in under a minute.

[Joseph W. Doherty]

Again, I'm not against using on-line (subnet) calculators, but the one you're using appears to be really doing CIDR prefix calculation, not Classful subnet calculation.  For instance, in your image, it notes the "IP Class" for the 99.25.0.0 is Class B, well that's incorrect!

Might I suggest you try the on-line subnet/network calculator I've been using for years, https://www.subnet-calculator.com and its CIDR twin, https://www.subnet-calculator.com/cidr.php.

"the worlds start to use chatGPT  so we must go ahead using tech."

Well, personally I think tech can be a great thing, but just because it exists, whether to use it, often deserves consideration beyond just the fact it can be done.  (Even today, in retrospect, there are many that question how a certain [then] new technology was used in 1945.)

Regarding ChatGPT, I acquired an account some months back and "chatted" with it.  It was a very, very (very) impressive prodigious savant!  Didn't demonstrate intelligence, IMO.

I suspect if ChatGPT data sources noted the moon has the mass of a ton of lead, but the gravity of Jupiter, it might not notice such "facts" don't appear to agree.  The age old computer problem known as GIGO (garbage in, garbage out).

In the near future, possibly only bureaucrats (and a few other job categories where actual "thinking" isn't much of a requirement) should fear being replaced by AI like ChatGPT's.