Mailinglist Archive: opensuse (3513 mails)

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Re: [opensuse] What's wrong with this IP address?
  • From: Robert Paulsen <robert@xxxxxxxxxxxxxxxxx>
  • Date: Thu, 8 Jan 2009 09:59:06 -0600
  • Message-id: <200901080959.06748.robert@xxxxxxxxxxxxxxxxx>
On Thursday 08 January 2009 9:48 am, Robert Paulsen wrote:
On Thursday 08 January 2009 9:36 am, Boris Epstein wrote:
On Thu, Jan 8, 2009 at 10:33 AM, Robert Paulsen

<robert@xxxxxxxxxxxxxxxxx> wrote:
On Thursday 08 January 2009 9:16 am, Per Jessen wrote:
250.146.71.215

See http://en.wikipedia.org/wiki/IP_address#IP_version_4_addresses

That will show you that the first octet of an ipv4 IP address can range
from

1 - 223

For classes A, B, and C.

Just out of the curiousity, is there any good rationale for having it
this way?

Look at the bit pattern in the 2nd column in the table that defines the
three classes:

A 0XXX XXXX
B 10XX XXXX
C 110X XXXX

I guess they might be able define additional classes:

D? 1110 XXXX
E? 1111 0XXX

etc. I don't know why it stops at A,B,C, but suspect it might have
something to do with routers and how they can break up address ranges to
direct IPs to different networks. This other bits might take on different
meanings.

Anyone know any better?

Bob

Thinking about this I note the following about "subnets" (defined by bit
masks):

CLASS CLASS BITS SUBNET BITS
A 0XXX XXXX 1111 1111 . 0000 0000 . 0000 0000 .
0000 0000
B 10XX XXXX 1111 1111 . 1111 1111 . 0000 0000 .
0000 0000
C 110X XXXX 1111 1111 . 1111 1111 . 1111 1111 .
0000 0000

After class C we run out of usable subnet bits (can't use all ones as that
would leave no bits to identify individual hosts).

Bob
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