Network Masks

I've never quite got my head around network masks although, generally
my home network performs fine.

I'm looking in to using the latest version of RealVNC which has a
security option to allow or disallow certain addresses but is seems to
require the format 0.0.0.0/0.0.0.0

Am I correct it assuming 192.168.1.1/255.255.255.0 would allow any
address from 192.168.1.1 up to 192.168.1.255 (Disallowing the certain
prohibited ones) whereas 192.168.1.1/255.255.255.255 would only allow
the exact address of 192.168.1.1

Geoff Lane



Geoff Lane

Geoff Lane wrote:
> I've never quite got my head around network masks although, generally
> my home network performs fine.
>
> I'm looking in to using the latest version of RealVNC which has a
> security option to allow or disallow certain addresses but is seems to
> require the format 0.0.0.0/0.0.0.0
>
> Am I correct it assuming 192.168.1.1/255.255.255.0 would allow any
> address from 192.168.1.1 up to 192.168.1.255

Correct.

(Disallowing the certain
> prohibited ones) whereas 192.168.1.1/255.255.255.255 would only allow
> the exact address of 192.168.1.1
>

Again , correct.

It gets a little bit more complicated when you use masks of other than 8 ,
16 , 24 or 32 bits and in that situation you would generally want to convert
into binary if calculating it yourself , or use a subnet calculator like
this one.

http://www.solarwinds.net/Tools/Free_tools/Subnet_Calc/
--
Alex

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"Geoff Lane" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> I've never quite got my head around network masks although, generally
> my home network performs fine.
>
> I'm looking in to using the latest version of RealVNC which has a
> security option to allow or disallow certain addresses but is seems to
> require the format 0.0.0.0/0.0.0.0
>
> Am I correct it assuming 192.168.1.1/255.255.255.0 would allow any
> address from 192.168.1.1 up to 192.168.1.255 (Disallowing the certain
> prohibited ones) whereas 192.168.1.1/255.255.255.255 would only allow
> the exact address of 192.168.1.1
>
> Geoff Lane
>

I'm not sure whether your first example needs to be
192.168.1.0/255.255.255.0 or it may simply be that using the .0 in the ip
address is merely the conventional way of entering the 192.168.1.1 -
192.168.1.254 range.

The second looks correct.

David.