ccna subnetting

sachinsharma

Hi everyone ,


Could anyone please tell me why do we need to subtract 2 while creating a sunetting like for ex(255.255.255.192=2^6 hosts and no.of subnet are 2^2-2=2)

redgunner

You always need a beginning, a range and an end

Let's look at a very simple to understand network (class c)

Okay let's pick a random host IP!!

Hostname: 192.168.1.64
11000000.10101000.00000001.01000000

Mask: 255.255.255.0
11111111.11111111.11111111.00000000

Let's find our Start Range and End Range (known as subnet and broadcast)
(The bold represents our network portion and the underline represents our host portion)

Subnet: 192.168.1.0
11000000.10101000.00000001.00000000

Broadcast 192.168.1.255
11000000.10101000.00000001.11111111

Okay so the range is 192.168.1.1 to 192.168.254 In this very basic example you can see you have 254 hosts in this 1 subnet.


Let's look another example

Subnet: 192.168.1.0
Mask: 255.255.254.0
Broadcast: 192.168.1.255

So this means you can have a range from 192.168.0.1 - 192.168.1.254 which is 510 hosts
Remember you need a beginning and an end!! (subnet and broadcast)

Imagine it ranging from 192.168.0.1 to 192.168.254.254 (It still only has 1 subnet and 1 broadcast)

Hope this makes sense

aristotle86

cool

AndersonSmith

redgunner wrote: »

You always need a beginning, a range and an end

Let's look at a very simple to understand network (class c)

Okay let's pick a random host IP!!

Hostname: 192.168.1.64
11000000.10101000.00000001.01000000

Mask: 255.255.255.0
11111111.11111111.11111111.00000000

Let's find our Start Range and End Range (known as subnet and broadcast)
(The bold represents our network portion and the underline represents our host portion)

Subnet: 192.168.1.0
11000000.10101000.00000001.00000000

Broadcast 192.168.1.255
11000000.10101000.00000001.11111111

Okay so the range is 192.168.1.1 to 192.168.254 In this very basic example you can see you have 254 hosts in this 1 subnet.


Let's look another example

Subnet: 192.168.1.0
Mask: 255.255.254.0
Broadcast: 192.168.1.255

So this means you can have a range from 192.168.0.1 - 192.168.1.254 which is 510 hosts
Remember you need a beginning and an end!! (subnet and broadcast)

Imagine it ranging from 192.168.0.1 to 192.168.254.254 (It still only has 1 subnet and 1 broadcast)

Hope this makes sense

Couldn't have said it any better!

Attempted Mustache

If you don't know already know, subnettingpractice.com (and similar sites) are very useful once you get the basics down.