Here's table showing the relationship between the / notation, the byte
notation, and the corresponding binary numbers (with a dot every eight
digits) for the 32 bit addresses.
/ Notation Binary Byte Notation
---------- ----------------------------------- --------------
/0 00000000.00000000.00000000.00000000 0.0.0.0
/1 10000000.00000000.00000000.00000000 128.0.0.0
/2 11000000.00000000.00000000.00000000 192.0.0.0
/3 11100000.00000000.00000000.00000000 224.0.0.0
/4 11110000.00000000.00000000.00000000 240.0.0.0
/5 11111000.00000000.00000000.00000000 248.0.0.0
/6 11111100.00000000.00000000.00000000 252.0.0.0
/7 11111110.00000000.00000000.00000000 254.0.0.0
/8 11111111.00000000.00000000.00000000 255.0.0.0
/9 11111111.10000000.00000000.00000000 255.128.0.0
/10 11111111.11000000.00000000.00000000 255.192.0.0
/11 11111111.11100000.00000000.00000000 255.224.0.0
/12 11111111.11110000.00000000.00000000 255.240.0.0
/13 11111111.11111000.00000000.00000000 255.248.0.0
/14 11111111.11111100.00000000.00000000 255.252.0.0
/15 11111111.11111110.00000000.00000000 255.254.0.0
/16 11111111.11111111.00000000.00000000 255.255.0.0
/17 11111111.11111111.10000000.00000000 255.255.128.0
/18 11111111.11111111.11000000.00000000 255.255.192.0
/19 11111111.11111111.11100000.00000000 255.255.224.0
/20 11111111.11111111.11110000.00000000 255.255.240.0
/21 11111111.11111111.11111000.00000000 255.255.248.0
/22 11111111.11111111.11111100.00000000 255.255.252.0
/23 11111111.11111111.11111110.00000000 255.255.254.0
/24 11111111.11111111.11111111.00000000 255.255.255.0
/25 11111111.11111111.11111111.10000000 255.255.255.128
/26 11111111.11111111.11111111.11000000 255.255.255.192
/27 11111111.11111111.11111111.11100000 255.255.255.224
/28 11111111.11111111.11111111.11110000 255.255.255.240
/29 11111111.11111111.11111111.11111000 255.255.255.248
/30 11111111.11111111.11111111.11111100 255.255.255.252
/31 11111111.11111111.11111111.11111110 255.255.255.254
/32 11111111.11111111.11111111.11111111 255.255.255.255
Here's and example of how to get from the binary number 11000000 to
the decimal number (192).
11000000 => 128*1 + 64*1 + 32*0 + 16*0 + 8*0 + 4*0 + 2*0 + 1*0
= 128 + 64 + 0 + 0 + 0 + 0 + 0 + 0
= 128 + 64
= 192
Another example (using an arbitrarily chosen binary number):
10000100 => 128*1 + 64*0 + 32*0 + 16*0 + 8*0 + 4*1 + 2*0 + 1*0
= 128 + 0 + 0 + 0 + 0 + 4 + 0 + 0
= 128 + 4
= 132
-----Original Message-----
From: David Lang [SMTP:[EMAIL PROTECTED]]
Sent: Thursday, June 10, 1999 9:51 PM
To: Jules
Cc: [EMAIL PROTECTED]
Subject: Re: IP significant bit addresses
-----BEGIN PGP SIGNED MESSAGE-----
the /number showes you the netmask. technicly it is the number of
"1"'s in
the netmask starting from the left (if the netmask was shown in
binary).
common examples are
/0 = 0.0.0.0 = all IP addresses
/8 = 255.0.0.0
/16 = 255.255.0.0
/24 = 255.255.255.0
/32 = 255.255.255.255 = one machine
this is most commonly used when you have an "odd" netmask for
subnet/supernets
A couple expamples That I use
/23 - 255.255.254.0 = 2 class C networks refered to as one network,
simplifies rules and gaines use of 2 IP addresses (the .0 and .255
in the
middle of the range are not special addresses)
/30 = 255.255.255.252 = 4 IP addresses, used for point-to-point
links (one
address is the network address, one for each end of the link, and
one
broadcast address)
David Lang
On Wed, 9 Jun 1999, Jules wrote:
> Date: Wed, 9 Jun 1999 19:12:32 +0800 (MYT)
> From: Jules <[EMAIL PROTECTED]>
> To: [EMAIL PROTECTED]
> Subject: IP significant bit addresses
>
>
> This is a newbie question, I've checked almost every resource
available to
> me, but I still don't really grasp this concept, so if anyone can
clarify
> it for me, I'd be grateful.
>
> How does one read addresses like 172.168.10/24 or 172.16.51.50/32
?
>
> In particular, what does the slash signify what does it do in the
above
> case(s).
>
> If this is anywhere off topic for the list, personal e-mail will
do too.
> Thanks in advance.
>
> Cheers!
> -J
>
> -
> [To unsubscribe, send mail to [EMAIL PROTECTED] with
> "unsubscribe firewalls" in the body of the message.]
>
"If users are made to understand that the system administrator's job
is to
make computers run, and not to make them happy, they can, in fact,
be made
happy most of the time. If users are allowed to believe that the
system
administrator's job is to make them happy, they can, in fact, never
be made
happy."
- -Paul Evans (as quoted by Barb Dijker in "Managing Support Staff",
LISA '97)
-----BEGIN PGP SIGNATURE-----
Version: PGP for Personal Privacy 5.0
Charset: noconv
iQEVAwUBN2CVqT7msCGEppcbAQHoMgf+PPFg3GLL+mkeUUoeFSsehp++hxllAp+5
1hpa7XuiWovdqIZXuE11iwk9bH44C7NF34RbXHgfDtN2H7BgLDxVoG/TDL7ReqLf
TozrjW+w6LQuMrjL3bf5R7A6riXeSI6RzICF1WVWecgtRjlU+6W8v67sc/OUYLiF
iZUW/ZSsOyLTAqh7gPdTJMEY1NONtD6gbddJ6z+NKZAgl+I7lWZaKTSm377kFc9T
EVwai7Ca+IwBNoXXb7x9XA6xraY6T+jXfT5xpyMCllbf2/dBYv16LENqal310h+d
d+JlatUqqQhrZCwciw/1NP1CeLCGmU77dmVC2ctgg8Gpiv8mRYZnTQ==
=rcWb
-----END PGP SIGNATURE-----
-
[To unsubscribe, send mail to [EMAIL PROTECTED] with
"unsubscribe firewalls" in the body of the message.]
-
[To unsubscribe, send mail to [EMAIL PROTECTED] with
"unsubscribe firewalls" in the body of the message.]
