[OT] CIDR Mask calculation
Jeff Vian
jvian10 at charter.net
Thu Oct 12 18:53:50 UTC 2006
On Thu, 2006-10-12 at 18:44 +0100, Rob Andrews wrote:
> On 12-Oct-2006 17:52.11 (BST), Dave Ihnat wrote:
> > Anyway, the addresses you gave, converted to binary, are:
> >
> > 219.128.0.0 : 11011011.10000000.00000000.00000000
> > 219.137.255.255: 11011011.10001001.11111111.11111111
> > ^
> > The last bit that is invariant between the two is marked with the caret;
> > converting back to a decimal dotted-quad (you can use 'dc' again--to set
> > the input to binary, simply change the 'o' operand in the above example
> > to an 'i', then input the binary value and print.)
> >
> > Mask
> > 255.240.0.0 : 11111111.11110000.00000000.00000000
> >
> > or, in conventional notation, 219.128.0.0/12.
>
> That's 219.138.0.0 - 219.143.255.255 though :)
>
Yep, as someone else already said, it cannot be done with a single
netmask. The desired range encompasses 2 subnets. or you have overlap
with other ranges as noted above.
> --
> rob andrews :: pgp 0x01e00563 :: rob at choralone.org
>
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