Accommodate 2000 hosts

Dear experts,

I am aiming to understanding network ID and hosts ID. I am quite good in binary numbers.

Suppose i need my new network to accommodate 2000 hosts.


I must have 11 bits in hosts id. which means:
Subnet mask:

suppose my network id is:

My problem really is to implement network addressing scheme and determine the broadcast ID

My idea:

Broadcast ID: Because all zero's in the third octet become all 1's.

First possible ip:
Last possible IP:

Am I correct?

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Thats correct. You will be using a class B address

Here is a cool site to play with
Bad idea.
No it is not correct.

Ethernet looses efficiency after 250-300 Hosts
Subnets should never go over the normal 254 Hosts segments created by a normal /24 bit mask.

The general rule is for every 200 Hosts create a new IP Segment.
So you have 2000 Host so you need 10 IP Segments

Stay far far away from the heavily overused "home user" addesses of 192.168.0.x or 192.168.1.x.
Start with 10 or higher in the third octet.  You could even start at 100.

Subnet 1  =  (,  254 Host capacity
Subnet 2  =  (,  254 Host capacity
Subnet 3  =  (,  254 Host capacity
Subnet 4  =  (,  254 Host capacity
Subnet 5  =  (,  254 Host capacity
Subnet 6  =  (,  254 Host capacity
Subnet 7  =  (,  254 Host capacity
Subnet 8  =  (,  254 Host capacity
Subnet 9  =  (,  254 Host capacity
Subnet 10  =  (,  254 Host capacity

Total capacity = 2,540 Hosts

A single LAN Router with at least Interfaces can easily do this by sitting in the logical center (hub & spoke layout).  the easiest way to do that is use a Layer3 Switch which is a Swithc and Router "crammed" into the same piece of hardware.   Use one with 48 ports and you can group at least 4 ports of the Switch into each Segment.

Then place Layer2 Switch out as the "ends" of the cable runs.

Below is a diagram showing this design.  It is a generic diagram and shows a 3-Segment LAN based on the design I am describing.

Typo from pasting.  Sorry.
The list should look like this:

Subnet 1  =  (,  254 Host capacity
Subnet  2  =  (,  254 Host capacity
Subnet  3  =  (,  254 Host capacity
Subnet  4  =  (,  254 Host capacity
Subnet  5  =  (,  254 Host capacity
Subnet  6  =  (,  254 Host capacity
Subnet  7  =  (,  254 Host capacity
Subnet  8  =  (,  254 Host capacity
Subnet  9  =  (,  254 Host capacity
Subnet  10  =  (,  254 Host capacity
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ozzycocaAuthor Commented:
thanks pwindell and snowwolf...i am very grateful for you interventions. what i am trying to achieve is strive very hard to understand this confusing stuff.

My querstion really doesnt say i have to divide the network into many subnets ( unless it is a rule, like pwindell said for example above). If it is not a rule or compulsory , all i want is just une network with 2000 hosts. Is this possible?

ozzycocaAuthor Commented:
Dear pwindell,
I am confused more after reading your answers, understand me ...i am a beginner.
All the subnets you mentionned above with that subnet mask ( will never be able to talk to each other while they are in the same network
for ex: Ip
           subnet mask: 255.255.255.o
the first ip will not talk to the second ip with the subnet mask is as mentionned.
I think it has to be:
Am i correct?
There is a difference between practice and theory. In theory, yes, you can have 2000+ hosts in the original setup. But in practice, its best to do what pwindell says.

Pwindells different subnets will talk to eachother because they connect to a router, and that basically is what a router does. It joins different subnets together.

Supernetting & Subnneting ..... Yes we can !!!

here is your equation: [ No. of hosts per subnet= (2^n ) - 2 ] , where n=No. of zeros in mask.
as we know, the subnet mask consistes of 1's from the left and 0's from the right

Lets go on now:
we want 2000 user per subnet ( suppose any IP class, let's use class B, as you mentioned)

so, 2000= 2^n -2    --->  2002 = 2^n  ---> take the log for this eqation to get n
so  n = log(2002)/log(2) =10.96  --> n should be integer number so we have to close it to the nearest integer which shoud be the higher ... here is 11

so to have 2000 user per subnet  we should have a mask with 11 zeros
which will be (

now we have the IP subnet: with mask will meet our requirements ( about 2048 user pre subnet)

here is our second and important step: which subnet we will use !!!  and how to calculate our usable IPs

look at the mask and find our intresting octet ( which is the 3rd) == we have 5 ones on it
let's calculate our step: no of subnets=  2^N where N= no of borrowed ones in interesting octet
so we may have 32 subnets ( 2^8) , so we will go on by step of 8

lets now calculate our first usable subnet: /21  which resides in the range  --to-->  ( firest subnet) --to--> (second subnet ) .. and so on.

for the first subnet:  ( subnetwork number , not used for users)  --to--> ( useable IP address for users and ur network devices) the last IP in subnet and is the broadcast ip for this subnet
now i finish

i wish i add you

My querstion really doesnt say i have to divide  the network into many subnets ( unless it is a rule, like pwindell said  for example above). If it is not a rule or compulsory , all i want is  just une network with 2000 hosts. Is this possible?

I don't always answer what was asked because people ask the wrong things because they have the wrong approach to a situation.  In such a case I answer what should have been asked and explain the right approach to getting the job done.

A subnet is a "network".  You can't put 2000 Host on a single network.  Long before you ever reached 2000 hosts the network would collapse to it's knees under the weight of the Browsdcasts and the Multicast traffic along with the Layer2 traffic like STP, CDP and others.

All the subnets you mentionned above with that subnet mask  ( will never be able to talk to each other while they are  in the same network
for ex: Ip
           subnet  mask: 255.255.255.o
the first ip will  not talk to the second ip with the subnet mask is as mentionned.
I  think it has to be:
Am i correct?

1. They are not on the same network.  You would have 10 networks in my description
2. The router in the center is what routes traffic between the networks

Dear pwindell,I am confused more after reading your answers,  understand me ...i am a beginner.

You are way over you head here it seems.  A company large enough to have 2000 Hosts would have to be insane to have a "beginner" build their system.  I'm not trying to be insulting, I'm really not, I'm just stating the facts.  Beginners do not build corporate networks.  Skilled trained and experienced network engineers build corporate networks while the beginners do what the skilled, trained, experienced engineers tell them to do.
If you read ozzycoca's profile, his details say

Member Profile:
i am a network technician student...

So Clearly he is not building a corporate network but trying to learn subnetting..
Member Profile:
i am a network technician student...

Ok,...well that is better then.
Then hopefully the diagram I gave and the details will be of some use to him.
Him being a student does not lessen what I described, fact it makes it more important that he know it and remember it for when he goes out in the real world.

But I don't read the profile of every person I respond to.  I might do over a hundred posts in a very short time.  I'm lucky to remember what I even wrote two days ago without rereading the thread over again each time before I add another reply.

Unfortunately, there are a lot of real situations out there where people are put in (or allowed to be in)  where they in no way have the skills to handle the job.  They create disasters out the wazzo and then "go away" leaving the mess for someone else to clean up.  In my "second job" with a consulting firm every thing I have had to do with them involves cleaning up messes (some very huge) that companies were left with, and we were asked to come in and straighten it out.
To aliadamz2010:

You math is correct.  But are you actually trying to tell him that is it "OK" to put 2000 host on a single IP Segment????

You need to clarify when you are talking about Supernetting routes in a routing table in the routers to carry the traffic across Backbone links between routers,...and when you are actually dealing with a Subnet full of individual network Hosts.

Don't let students go off into the real world with ideas in their head that it is "OK" to do something that is just plain horrible.  The world of IT is already in enough of a mess as it is.
Dear pwindell,
what understand from the question is that the auther wants to know the is it possible to do this ,, and how he can define the users and the BC address ,, i mean subnetting. and i explain this to him

second thing ( and due to my work) the bandwidth , routing , throughput is important factor  in devices you own. and then you can decide if your devices can carry 2000 hosts or not

but due to ur design and security requirements in real world i will not put 2000 host on one subnet

so i was explaining that its possible to ,,, and explain how  ,, so its the way to do subnetting as i understand from the questions

and after that ,, ur network requirement is what put the restrictions that make you think of how to do subnetting
The limits on hosts per segment is not about the equipment handling it and is not about "choices" that you can make or not make.

It has to do with Ethernet as a technology and the way if functions.  You cannot efficiently run 2000 Host on a single segment, makes no difference on what equipment you use and is not something you can arbitrarily choose to do or not do because you want to or don't want to.

Your math is correct.  But creating a Net ID and Mask to cover 2000+ hosts is only done with Supernetting over a backbone when there are the proper sequentialy numbered Host Subnets down stream on the other side of the next router(s).  When it finally reaches the Host Segments it all needs broken down into segments of 254 Hosts or less.  This needs to be made clear,...and it is probably even more important than just knowing what you get on the host side of an address by sliding the mask around.  

New students need to know this and unfortuneately the industry seems full of people already working in it  who don't comprehend this (I'm not saying you are one).  If I hired someone who then tried to overload a customer's network with a bad design like that I would fire them on the spot.   This stuff is one of the first things I would "probe" the minds of potential new employees to see if they had it straight.  If they don't have that correct then there is probably a whole bunch else they don't have right.
again ,, i was explain an idea but for design i will not go with something like this .. coz of security needs in my mind at least.

and any way its nice to meet you here

ozzycocaAuthor Commented:
Thanks Pwindell and others for your contributions.
AS i said before, i am just trying to learn about Subnetting,etc.

Please guys, how can i implement this solution using SERVER 2003 with DHCP installed.
I was trying to do it, but i am a little bit confused when i had to provide only one scope , despite having many subnets. I should have done it this way for example:

Starting IP:
Ending IP:
Default Gateway (router): 192.168.X.Y

Is this OK?
To create a Supernet for backbone routing purposes this would be an example below.
This is only in the routing tables of the routers.  The actual backbone links themselves and the routers will use a 30 bit mask ( run 4-address, 2-host segments between the routers.  As it gets closer to the last router, as is it goes hop by hop along the way, it will start splitting off "chunks" of it.  By the time the end routers are reached at the actual network segments that have actual Hosts (PCs) in them they will be 254-Host segments or smaller.   Keeping track of the routing nightmare is the job of Routing Protocols such as RIP, IGRP, OSPF, etc, a human is probably never going to manually create something like this anyway.

Mask = (
ID =
BCast =
Range = --
2,048 address, minus the ID and BCast = 2,046 usable addresses

The full breakout of the full list of possible 2,048 address networks based on the RFC 192.168 network would be this below.
The first address of each row is always the Net ID
The last address of each row is always the Broadcast
All address between them (on each row) are the Usable Addresses

Supernet 1    192.168.0    ---    
Supernet 2    ---    
Supernet 3    ---    
Supernet 4    ---    
Supernet 5    ---    
Supernet 6    ---    
Supernet 7    ---    
Supernet 8    ---    
Supernet 9    ---    
Supernet 10    ---    
Supernet 11    ---    
Supernet 12    ---    
Supernet 13    ---    
Supernet 14    ---    
Supernet 15    ---    
Supernet 16    ---    
Supernet 17    ---    
Supernet 18    ---    
Supernet 19    ---    
Supernet 20    ---    
Supernet 21    ---    
Supernet 22    ---    
Supernet 23    ---    
Supernet 24    ---    
Supernet 25    ---    
Supernet 26    ---    
Supernet 27    ---    
Supernet 28    ---    
Supernet 29    ---    
Supernet 30    ---    
Supernet 31    ---    
Supernet 32    ---    


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The actual backbone links themselves and the routers will use a 30 bit  mask ( run 4-address, 2-host segments between the  routers.

This could be larger segments if it is not a "point-to-point" situation.

I cannot account for every variation and possibility that might exist in my posts.
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