Private Vs. Public Addresses - Alcatel speed touch home Advanced User's Manual

9.1.2

Private vs. Public Addresses

3EC 17096 AAAA TCZZA Ed. 01
In the examples throughout this document Private IP addresses are
used for local IP configurations. Private IP addresses are defined in
RFC1918 Address Allocation for Private Internets. This RFC is
categorized as "Best Current Practice".
Private hosts do not require access to hosts in other enterprises or
to the Internet. Therefore it is sufficient for the host to have an IP
address that is unique within the enterprise but may be ambiguous
between enterprises and on the Internet.
Private IP Address:
"
In principle if an IP address is assigned to a host and the
connectivity is limited to intra enterprise communication only,
the IP address can be assumed to be privately held.
The limitation however is that communication between
enterprises and connection to the Internet itself via those private
IP addressed PCs is not possible and even not allowed.
Public IP Address:
"
Is an officially assigned IP address by an Internet Registry and
is guaranteed to be worldwide unique. As a consequence
the host to which the address is assigned has worldwide
Internet connectivity.
IANA (the Internet Assigned Number Authority) defined blocks of
IP addresses for private purposes:
Table 7 IP Address Blocks used for Private Purposes Only
From: To:
10.0.0.0 10.255.255.255
172.16.0.0 172.31.255.255
192.168.0.0 192.168.255.255
Addressing purpose:
1 Class A network number
16 contiguous Class B network
numbers
256 contiguous Class C network
numbers
9 Configuring IP
81 / 180