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Full Discussion: Subnetting
Special Forums IP Networking Subnetting Post 302993570 by drysdalk on Saturday 11th of March 2017 07:41:05 AM
Old 03-11-2017
Hi,

Firstly, from just looking at a single IP, you can't tell how large the network it's a part of is. You need to know the netmask. So for example, if I had an IP of 192.168.1.10, that doesn't tell you anything at all about how large or small the network I'm a part of is.

But if I tell you the netmask - e.g. 192.168.1.10/24 or 192.168.1.10/255.255.255.0 - then you know it's part of a network of 256 addresses, running from 192.168.1.0 to 192.168.1.255.

If on the other hand I'd told you the netmask was 192.168.1.10/25 or 192.168.1.10/255.255.255.128 - then you'd know it was part of a network of 128 addresses going from 192.168.1.0 to 192.168.1.127.

And again, in every network, the very first address and the very last address are not usable for hosts, as they are reserved for other purposes.

You can also get plenty of other netmasks than the old simple Class A, B, C notation tells you. For instance I could just have easily told you my netmask was 192.168.1.10/28, in which case you'd then be able to calculate that the network I was a part of runs from 192.168.1.0 to 192.168.1.15, and conists of 16 IP addresses.

So just from looking at an IP you can't tell anything about the size of the network. And these days, there are far more netmasks and subnet sizes that are far more common than the old Class A/B/C notation.
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LEARN ABOUT OPENSOLARIS

whois

whois(1)							   User Commands							  whois(1)

NAME

       whois - Internet user name directory service

SYNOPSIS

       whois [-h host] identifier

DESCRIPTION

       whois  searches	for  an  Internet directory entry for an identifier which is either a name (such as ``Smith'') or a handle (such as ``SRI-
       NIC''). To force a name-only search, precede the name with a period; to force a handle-only search, precede the handle with an  exclamation
       point.

       To  search  for	a  group or organization entry, precede the argument with * (an asterisk). The entire membership list of the group will be
       displayed with the record.

       You may of course use an exclamation point and asterisk, or a period and asterisk together.

EXAMPLES

       Example 1 Using The whois Command

       The command:

	 example% whois Smith

       looks for the name or handle SMITH.

       The command:

	 example% whois !SRI-NIC

       looks for the handle SRI-NIC only.

       The command:

	 example% whois .Smith, John

       looks for the name JOHN SMITH only.

       Adding ... to the name or handle argument will match anything from that point; that is, ZU ... will match ZUL, ZUM, and so on.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWrcmdc 		   |
       +-----------------------------+-----------------------------+

SEE ALSO

       attributes(5)

SunOS 5.11							    6 Nov 2000								  whois(1)
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