Subnetting Post: 302993570

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Special Forums IP Networking Subnetting Post 302993570 by drysdalk on Saturday 11th of March 2017 07:41:05 AM

03-11-2017

Registered User

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 XFREE86

whois.conf

WHOIS.CONF(5)							 Debian GNU/Linux						     WHOIS.CONF(5)

NAME

       whois.conf - alternative WHOIS servers list for whois client

SYNOPSIS

       /etc/whois.conf

DESCRIPTION

       This file contains a list of WHOIS servers which can augment or override the built-in list of the client.

       It's  a plain text file in ASCII encoding. Each line consists of two fields: a pattern to match WHOIS object identifier and a corresponding
       WHOIS server domain name.

       Fields are separated by non-empty sequence of space or a tabular characters.  A line starting with a hash character is a free  comment  and
       it's not considered.

       The  pattern is case-insensitive extended regular expression if whois client has been compiled with POSIX regular expressions support. Oth-
       erwise, simple case-insensitive suffix comparison against WHOIS object identifier is used.

       Internationalized domain names (IDN) must be specified in ascii-compatible encoding (ACE) format.

EXAMPLE

       .nz$		 nz.whois-servers.net
       # Hangul Korean TLD
       .xn--3e0b707e$	 whois.kr
       # Private ASNs
       ^as645(1[2-9]|2[0-9]|3[0-4])$	whois.example.net

FILES

       /etc/whois.conf

SEE ALSO

       whois(1)

AUTHOR

       This manual page was written by Petr Pisa <ppisar@redhat.com> and is licensed under the terms of the GNU General Public License, version  2
       or higher.

Petr Pisa							   9 April 2013 						     WHOIS.CONF(5)

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whois.conf