From: Petr Lapukhov (petrsoft@gmail.com)
Date: Sat Apr 01 2006 - 13:13:53 GMT-3
Hello,
i guess you could distinguish all EVEN IP addresses on subnet with
200.200.1.0 0.0.0.30
30 = 00011110
Here's how it basically works:
inverse mask determines which bits in nework address
are "locked" and which are not.
So you take subnet mask, and detemine what portion
of address is "locked" aready : in our case we have first 27 bits
fixed (network part). So far, first 27 bits in inverse mask are zeros
from very beginning.
Now, looking at last five bits (host portion).
We need to set last bit to zero (to make host number EVEN).
So we set last bit in host portion of network address to zero,
and last bit in inverse mask to zero too.
(If we were required to select ODD ip address, we would have
to set last bit in host portion to one, and last bit in inverse mask to
zero.
e.g. 200.200.1.1 0.0.0.30)
Every over bit in host portion of address may take any value, so
the rest four bits in inverse mask are "ones".
HTH
Petr
2006/4/1, Radioactive Frog <pbhatkoti@gmail.com>:
>
> Hi Group,
>
> This is very basic question but I am confussed.
>
> Network 200.200.1.0 with subnet mask is 255.255.255.224.
>
> How can we create a ACL to permit only even IP address ?
>
> Thanks
>
> Frog.
>
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