# Help on subnet calculation.

Member Posts: 66 ■■□□□□□□□□
Help on subnet calculation.
Let’s say you have a network address for example, 192.168.1.0/24.
-there are 40 different subnets with 10 computers on each subnet and you have an intention to add not more than 10 more subnet in the future.
-the IP address of one server in your domain is 198.168.1.10 and a default gateway 192.168.1.5.
-How do you calculate the subnet mask?

Any one with a website or articles that deal with the above explicitly?
I mean with calculations and detailed explanations (decimal & binary).

I’ve been reading this subnetting thing for three days now and it’s not sinking into my small brain completely.

I know from comments from those who have written this exam that, this topic is not a major focus but as they advice, “it is better to prepare for everything”.
“Be generous without thought of reward”.
“It takes two to see both sides of a Problem”.

• Member Posts: 356
@Ricardo1

-there are a lot of subneting questions in the real exam . Is better to know , because subnetting will apear in CCNA to.

how you saied you have 192.168.1.0/24 , network.Now you can just subnet it like you want.

In you example , you have a maximum of 254 usable addreses ( not considering network and broadcast address , and of course not considering subneting ).
there are 40 different subnets with 10 computers

-something fishy ..how can it be more than 400 usable addreses ? on 192.168.1.0/24 ? 10 computer's per subnet mean's 40*10=400.
-adding no more than 10 subnet's ? it mean's 500 ( and with broadcast and network addresses , it will pass 510 to ) , meaning that you need more that 192.168.0.0-192.168.1.255.

You can aford something like B class , 172.16.0.1-172.16.2.100 ( I mean this segment will acomodate your need for subneting and computer's per subnet ).
the IP address of one server in your domain is 198.168.1.10 and a default gateway 192.168.1.5.

-only with the indication's you sayed to us , the subnet mask is 255.255.255.0 , you mean 192.168.1.0/24.

I think you may not understand a think , really , I can give you an example , to get the idea and the ask [ur=www.google.com] Google is your friend[/url].

Let's take 192.168.1.0/24 network.

We want 4 subnet's .HOW do we make this thing ?

/24 = 255.255.255.0 = 11111111.11111111.11111111.00000000

meaning 8 of 0 => 2 at power eihgt meaning 256 hosts ( 256-2 usable host's ).So you want 4 subnet's ? We should share the usable host between them and make 256/4 = 64 ( 64-2 host per subnet ).Meaning that we need only 6 of 0 in the subnet mask.We make the first 2 zero's in one's meaning 11111111.11111111.11111111.11000000=255.255.255.192 = /26.

So we can make this :

first net : 192.168.1.0-192.168.1.63
second : 192.168.1.64....
..fourth..

Hey try this to : Search this forum

Optimism is an occupational hazard of programming: feedback is the treament. (Kent Beck)
• Member Posts: 2,112 ■■■■□□□□□□
Ricardo1 wrote:
Help on subnet calculation.
Let’s say you have a network address for example, 192.168.1.0/24.
-there are 40 different subnets with 10 computers on each subnet and you have an intention to add not more than 10 more subnet in the future.
-the IP address of one server in your domain is 198.168.1.10 and a default gateway 192.168.1.5.
-How do you calculate the subnet mask?

Any one with a website or articles that deal with the above explicitly?
I mean with calculations and detailed explanations (decimal & binary).

I’ve been reading this subnetting thing for three days now and it’s not sinking into my small brain completely.

I know from comments from those who have written this exam that, this topic is not a major focus but as they advice, “it is better to prepare for everything”.

192.168.1.0/24 is a standard class c address that has 24bits network, 8 bits host.Therefore 256-2=254 hosts addresses.
You want 40 subnets and 10 hosts.For 40 in 2s complement
2,4,8,16,32,64 so to have 40 subnets you need to borrow 6 bits, this will give a max of 64 subnets but the lower option 32 is too small.The problem now is you only have 2 bits available for hosts. 2^2-2 = 2 available hosts.
So with the specifications you gave its not possible, hope you can see where i'm coming from and try yourself.
Networking, sometimes i love it, mostly i hate it.Its all about the \$\$\$\$
• Member Posts: 10,090
Ricardo1 wrote:
Any one with a website or articles that deal with the above explicitly?
I mean with calculations and detailed explanations (decimal & binary).

Try the LearnToSubnet web site. Once you've gone through that tutorial, you may understand subnetting and the answers you've been given to that specific example you asked about.
:mike: Cisco Certifications -- Collect the Entire Set!
• Inactive Imported Users Posts: 74 ■■□□□□□□□□
Also, read up on Supernetting and VLSM's.
• Member Posts: 66 ■■□□□□□□□□
Thanks a million Gurus for explanations and links.
I'll try my hands on them.

The above was just an example.

Much apreciated
“Be generous without thought of reward”.
“It takes two to see both sides of a Problem”.