IP address format

[Roady]

Hi can anyone help me!!!

I came accross an IP address of 192.168.81.0/27, in a forum, What does the 27 figure indicate??

Thanks all

[PrntRhd]

Actually this is a LAN question.
The range of addresses in the example are from 192.168.81.0--192.168.81.27 so 28 addresses in that range.
27 would be the 28th address.

[juniper]

since classful routing on the internet is gone it now uses a classless IP scheme meaning that the subnet mask which is made up of 32 bits can be seperated at any point now not just at the classful boundaries of the past like a class C was 255.255.255.0 which is /24 or 24 bits of the 32 bit range so to answer your question it means that they are using 27 of the 32 bits to define the subnet mask. /27 = 255.255.255.224 this is what is meant when an ISP says they will give you a slash 27 (/27)

[Jiggy]

Give these 3 pages a read over, its what im reading for Network+.

http://www.firewall.cx/supernetting-intro.php

[Roady]

Thanks everyone much appreciated!!