IP Addressing

[litass123]

hi, i'm noob here.

Just have a question for all experts.

what is the meaning of this -> 10.150.10.5/32 ??

The "/" means what?

[pkhatri]

Hi,

The number following the slash indicates the size of the mask. So if the number is 32, it means that the subnet mask contains all ones, which makes it a host route.

In binary, the /32 gives you:

11111111 11111111 11111111 11111111

which becomes 255.255.255.255 in dottec-octet format.

Similiarly, in binary, /24 gives you:

11111111 11111111 11111111 00000000

which becomes 255.255.255.0 in dottec-octet format.

The slash notation is typically referred to as the CIDR format of expressing subnet masks. CIDR = Classless InterDomain Routing.

Pls do remember to rate posts.

Paresh

[litass123]

Hi, Paresh,

So In binary, the /16 is becomes 255.255.0.0 ??

how about /20 ??

[pkhatri]

That is correct..

/20 gives you 11111111 11111111 11110000 0000000

which gives you 255.255.224.0

Pls do remember to rate posts.

Paresh

[kar.bibhu]

Hi Paresh I think it sud be .240 and not .224.

Please confirm.

Thanks

Bibhudutta Kar,

Cable and Wireless.

[kar.bibhu]

Hi

if its /20 then the subnet mask will be some thing like 255.255.240.0. To calculate the CIDR formay u have to know the binary to decimal conversion and vice-versa. The shortcut for that is 128, 64,32,16,8,4,2,1. As you go on increasing the mask bits just add the numbers starting from 128 till the number of bits used for masking. And the final sum will be your network mask for the given CIDR address.

Thanks and regards,

Bibhudutta Kar,

Cable and Wireless.

[Patrick Laidlaw]

Hello,

You are right a /20 will be 255.255.240.0 and not 224. Paresh was probably just typing to fast.

Patrick

[pkhatri]

Thanks Patrick - my brain and my typing get out of sync sometimes.. this was one of those times !

Paresh