On 07/07/2011 04:38 PM, lkrawczyk@amhealthgroup.com wrote:
>
> We've just puchased Cox Business Internet and I have been assigned a 
> CIDR block.  I have no experience with this.  In the past I've been 
> assigned a range of IPs that I basically forward from the external 
> interface through the internal interface using iptables on a dedicated 
> Linux box.  I have multiple logical external and internal interfaces.  
> The internal interfaces point at LANs using 192 subnets.
>
> What I'm confused about now is that my static ip is 70.xxx.xxx.xxx and 
> my CIDR block is 24.yyy.yyy.yyy/28.  Since the CIDR block is being 
> routed through my static IP I don't really know what the external 
> interface configuration should be.
>
> Does anybody have any experience with this?
>
> Thanks.
>

CIDR block is really easy, /28 means the first 28 bits of your subnet 
mask are 1's and the remaining 4 are 0.  So your subnet mask is:
255.255.255.240.  So, it that address were 123.123.123.112/28, your 
network would be 123.123.123.112, your hosts would be 
123.123.123.113-126, and your broadcast would be .127

Hope that helps
Kevin Fries