On Thu, Jan 8, 2009 at 10:59 AM, Robert Paulsen
On Thursday 08 January 2009 9:48 am, Robert Paulsen
On Thursday 08 January 2009 9:36 am, Boris
On Thu, Jan 8, 2009 at 10:33 AM, Robert Paulsen
On Thursday 08 January 2009 9:16 am, Per Jessen
That will show you that the first octet of an ipv4 IP address can range
1 - 223
For classes A, B, and C.
Just out of the curiousity, is there any good rationale for having it
Look at the bit pattern in the 2nd column in the table that defines the
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
Anyone know any better?
Thinking about this I note the following about "subnets" (defined by bit
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).
Class D is used for Multi-cast and thus does not support TCP. UDP is
fine. Not real common, but say you have a decent size LAN and you
want to "broadcast" something across it, you can designate one of the
Class D's for that.
I looked into doing NTP style broadcasts that way a few years ago.
The issue is that every switch / router in the lan/wan you need to
forward the multi-cast packets through has to be configured to do so.
I think some brokerage firms broadcast out various news shows to the
traders desktops via IP broadcast mechanisms. I assume they use Class
D packets to carry the UDP packets. (ie. If a trader wants to see
what Fox News is showing, they have a video app on their desktop that
can tune into the multi-cast packets and show it to them.
Class E I know of no use for, but I would not rule it out.
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