Subnetting help PLEASE PLEASE PLEASE!

Ricochet J

Ricochet J

Ricochet J

Soldato
Joined
29 Jun 2004
Posts
12,957
Hey! I believe I have subnetting NAILED apart from one thing. How the hell do I translate the numbers i've got into a readable address, like aaa.bbb.ccc.ddd?

Let me give you an example.

Ip adress 192.168.10.0 SubnetMask 255.255.255.192
^^ Basically subnet that!

Okay, this is the way I do it.

1) How many subnets?
2) How many hosts per subnet?
3) Valid subnets?
4) Broadcast address for each subnet?
5) Valid hosts on each subnet?

So, for our example:

1) How many subnets?
2^2 = 4 Subnets

2) How many hosts per subnet?
2^6 - 2 = 30 hosts per subnet

3) Valid subnets?
256 - subnet mask
256 - 192 = 64
Subnets: 0, 64, 128, 192

4) Broadcast address for each subnet?
Subnet 0: Broadcast - 255.255.255.63
Subnet 64: Broadcast - 255.255.255.127
Subnet 128: Broadcast - 255.255.255.192
Subnet 192: Broadcast - 255.255.255.255

5) Valid hosts on each subnet?
Subnet 0: hosts :- 1 - 62
Subnet 64: hosts :- 65 - 126
Subnet 128: hosts :- 129 - 191
Subnet 192: hosts :- 193 - 254

Right, to make it easier for you, i'll put this all in a simple table form

Subnet 0
Broadcast 255.255.255.63
hosts 1 - 62

Subnet 64
Broadcast 255.255.255.127
hosts 65 - 126

Subnet 128
Broadcast 255.255.255.192hosts 129 - 191

Subnet 192
Broadcast 255.255.255.255
hosts 193 - 254



HOW THE HELL DO I USE THE ABOVE INFO AND TRANSLATE IT INTO AN ADDRESS LIKE AAA.BBB.CCC.DDD? ARRRGGGGHHHHHHHHHHHHHHHHHHHH!

Help! :p
 
well because it is a Class C address you are using and the subnet mask is 255.255.255.x... you would have an address like 192.168.10.1 to 192.168.10.62 for subnet 0 and so on.

If you have "255" in a portion of a subnet mask, that it the network part of the subnet, which does not vary between addresses...

i.e. 192.168.1.0 is a class c address. so subnet will be 255.255.255.xxx.... that means 192.168.1 is always the same.. and only the 0 portion will vary.... hope that makes some sense
 
Last edited:
This website might help you. SImply type in an IP address and a slash notation (for example 192.168.0.1/24) and click New Lookup.

You'll be given the subnet, the IP's, the broadcast IP and so on.
 
You have basically answered it yourself in this segmant.

Ricochet J said:
Subnet 0
Broadcast 255.255.255.63
hosts 1 - 62

Subnet 64
Broadcast 255.255.255.127
hosts 65 - 126

Subnet 128
Broadcast 255.255.255.192hosts 129 - 191

Subnet 192
Broadcast 255.255.255.255
hosts 193 - 254
Click to expand...

Example

Subnet 0
Broadcast 255.255.255.63
hosts 1 - 62

IP ADDRESS: 192.168.10.x (x been the host usable address)
IP ADDRESS = 192.168.10.1 TO 192.168.10.62
SUBNET = 255.255.255.0

you get me?

Another example

Subnet 64
Broadcast 255.255.255.127
hosts 65 - 126

IP ADDRESS: 192.168.10.x (x been the host usable address)
IP ADDRESS = 192.168.10.65 TO 192.168.10.126
SUBNET = 255.255.255.64
 
I work from memory on subnetting as I work for an ISP, once you memorise stuff theres no need to write it out, its simpler from slash notation.

/32 host address
/30 block of 4
/29 block of 8
/28 block of 16
/27 block of 32
/26 block of 64
/25 block of 128
/24 block of 255
/23 block of 512
/22 block of 1024
/21 block of 2048
/20 block of 4096
so on so fourth..

If its class C your only up to /24 anyways, so just memorise the subnet masks and you can figure everything out.. for example if you had 192.168.10.49/26 you'd know that network is subnetted into blocks of 64, so the networks would be
192.168.10.0
192.168.10.64
192.168.10.128
192.168.10.192

Therefore it would belong to the first block.

If your messing around with bigger bits of address space, say a block of 2048 addresses or a /21

You could have host 192.168.49.36/21

Blocks would be:

192.168.0.0/21 mask 255.255.248.0
192.168.8.0/21 mask 255.255.248.0
192.168.16.0/21 mask 255.255.248.0
192.168.24.0/21 mask 255.255.248.0
192.168.32.0/21 mask 255.255.248.0
192.168.40.0/21 mask 255.255.248.0
192.168.48.0/21 mask 255.255.248.0
192.168.56.0/21 mask 255.255.248.0

so the 192.168.49.36 host would belong to the 7th subnet..

Sorry if some of this is wrong, just going off the top of my head..
 
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