B C
/16 /24 0
/17 /25 128
/18 /26 192
/19 /27 224
/20 /28 240
/21 /29 248
/22 /30 252
/23 /31 254
/24 /32 255
Craig Gittens
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of MIke Mckay
Sent: Monday, May 21, 2001 3:07 PM
To: [EMAIL PROTECTED]
Subject: Re: [IMail Forum] Notation conversion
I have a reasonable knowledge (not fantastic) of binary maths and TCP-IP but
have only ever seen slash notation once on a router which needed a full
class C range setting up so this was a straight forward 255.255.255.0 /24.
Our ISP gave me the three ranges shown as their full range that is allocated
for their dial up service, which needs to be added on the smtp security page
to the relay for setting to tell imail which ips it is allowed to forward
mail for to avoid spamming as we were recently added to orbs.
Where this is out of my expertise is as you mentioned the fact, that I know
how to subnet a class A in the second octet a class B in the third and a
class C in the fourth. But this is class B subnetting on a class C or a
group of 64 class C ranges from 212.1.128.1 up to 212.1.192.255.
But this method of subnetting up from a class in the previous octet to
combine several consecutive ranges is new to me and as IMAIL will not let me
enter the ranges as I was given them I need to find out how they are
represented in dotted notation.
Apologies if I didn't explain the problem in enough detail
Thank you
Mike
----- Original Message -----
From: "R. Scott Perry" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Monday, May 21, 2001 7:46 PM
Subject: Re: [IMail Forum] Notation conversion
>
> >What is the correct dotted notation for the following what I think it
> >should be is in brackets but a few of the online subnet calculators say
it
> >is incorrect for a class C, but this is all my isp has given me and IMAIL
> >will not accept /xx notation,
> >
> >212.1.128.0/19 (255.255.224.0)
> >212.157.128.0/18 (255.255.192.0)
> >212.159.128.0/17 (255.255.128.0)
>
> The first set of numbers is the beginning IP address (212.1.128.0). The
> number after the "/" is the number of bits common to all the IP addresses
> (the first 19 bits of 212.1.128 are always the same; that is, it's always
> 212.1. followed by a numer starting with 100xxxxx in binary. The subnet
> mask -- 255.255.224.0 is just a bunch of 1's (equal to the /19) followed
by
> a bunch of 0's (32 minus the number of 1s).
>
> >but as it is subnetted in the 3rd octet shouldn't they all be shown as
> >XXX.XXX.0.0 ?
>
> Shown where? A "/16" would be a Class B, a "/24" would be a Class
> C. These are inbetween a Class B and Class C in size.
>
> Where are you trying to enter these numbers in IMail? I don't believe
> IMail has anywhere you can enter IP ranges using the /xx notation.
>
> If you're familiar with binary numbering, this should seem straightforward
> once you grasp it. If you aren't familiar with binary numbers, it's
> probably best just to ask someone, as it may be very hard to understand
> otherwise.
>
> -Scott
>
> Declude: Anti-spam and Anti-virus solutions for IMail.
http://www.declude.com
>
>
>
> Please visit http://www.ipswitch.com/support/mailing-lists.html
> to be removed from this list.
>
> An Archive of this list is available at:
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>
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