Range of IP addresses

[taubate]

Can someone explain how does a network end up with a range of IP addresses? How does it get set up this way?

 

[ChrisAC]

You apply to your ISP for a range. ************************
Chris Andrew, CCNA
chris@iproute.co.uk
************************

 

[zephan]

Hi taubate,
I hope I got the question
You know an IP is componed by a network number and a host number, and that is defined by the IP nb + the subnet mask.

eg : subnet mask = 255.255.255.0

if your IP is : 213.20.60.49 that mens your subnet nb is 213.20.60 and the host nb is 49.
Well, basicly it's the subnet mask that defines the IP range, in the sample case, your IP range is from 213.20.60.1 to 213.20.60.254

I feel that is too much simple, is it really what you meant ?

 

[taubate]

iproute - thanks.

zephan - Yes, you answered my question. Which leads me to 2 other questions:

1) Who and how is the subnet mask determined?
2) Of the 4 components of the IP address, say 213.20.60.49, is the last component (the 49) always the host number?

Thanks for your help.

 

[zephan]

Hi,

In facts IP adress is a serial of 4 binary numbers, each one is coded on 8 digits. And so is the subnet mask.
So 255.255.255.0 is :

1111 1111.1111 1111.1111 1111.0000 0000

Well, the part of IP corresponding to '1's is the net number, and the part corresponding to '0's is the host number.

Now, how to define the subnet mask; you can refere to this rule : if you have got a great number of networks whit a small number of hosts in each one, you'll have to put lot of '1's right of the subnet mask.

With the sn mask sample above, you'll be able to adress thousands networks & 253 hosts in each one.

If you have a small number of networks with thousands hosts in each one, the number of '1's in your sn mask will be reduced :

with 255.0.0.0 as subnet mask, you'll be able to adress 253 subnets with thousands hosts in each one (without considering restrictions on networks classes)

Hope will help

 

[taubate]

Zephan - thanks again!