ip address question

[phillosophy]

when an example specifies a network ip address such as

[Mamour]

They are called masks. Essentially, writing 168.109.1.10/28 means that you take 168.109.1.10 as base address but let the last 4 bits (out of 32, which comes from 32-28 ) change freely.

In practice, if you take the 168.109.1.10 address, the last byte of the adress (here represented by 10) would be 00001010 in binary notation. These last 4 numbers are the 4 bits that are allowed to changed with the /28 mask. Thus, they can take any value of 0 or 1. Using this mask would thus generate all adresses where these last 4 bits are between 0000 and 1111 in binary notation, which translates to 0 and 15 in decimal notation.

168.109.1.10/28 thus stands for all adresses from 168.109.1.0 to 168.109.1.15 (2^4 = 16 addresses).

The same thing can be applied for the /8 mask, where the 24 last bits are allowed to change (effectively representing the last 3 IP numbers, as each numer separated by a dot represents one byte, or 8 bits). You'd then generate all adresses from 168.0.0.0 to 168.255.255.255 (2^24 = 16,777,216 adresses).

This can be pretty daunting at first, but don't hesitate to ask if you don't get it!

Cheers,
_________________
//Markus.

[Earthwings]

Moved from Installing Gentoo to Networking & Security.