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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 SUSE

tgt-setup-lun

tgt-setup-lun(8)					      System Manager's Manual						  tgt-setup-lun(8)

NAME

       tgt-setup-lun - creates a target, adds a device to the target and defines initiators that can connect to the target

SYNOPSIS

       tgt-setup-lun -d device -n target_name [initiator_IP1 initiator_IP2 ...] [-h]

DESCRIPTION

       Starts tgtd if necessary and creates a target according to the supplied target_name. The format of the target name is as follows:
       iqn.2001-04.com.<hostname>-<target_name> The target name must be unique.

       The  script then adds the requested device to the target. If specific IP addresses are defined, it adds them to the list of allowed initia-
       tors for that target. If no IP addresses is defined, it defines that the target accepts any initiator.

EXAMPLES

       Create a target that uses /dev/sdb1 and allows connections only from 192.168.10.81:
       tgt-setup-lun -d /dev/sdb1 -n my_target 192.168.10.81

       Create a target that uses /dev/sdb1 and allows connections only from 192.168.10.81 and 192.168.10.82:
       tgt-setup-lun -d /dev/sdb1 -n my_target 192.168.10.81 192.168.10.82

       Create a target that uses /dev/sdb1 and allows connections from any initiator:
       tgt-setup-lun -d /dev/sdb1 -n my_target

       Display help:
       tgt-setup-lun -h

AUTHOR

       Written by Erez Zilber

REPORTING BUGS

       Report bugs to <erezz@voltaire.com>.

COPYRIGHT

       Copyright (C) Voltaire Ltd. 2008.

																  tgt-setup-lun(8)
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