Hirschmann GREYHOUND GRS1020, Справочное руководство

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Specifying the IP parameters
2.1 IP parameter basics
43
UM Config GRS
Release 8.0 09/2019
The first byte of an IP address is the network address. The worldwide leading regulatory board for
assigning network addresses is the IANA ("Internet Assigned Numbers Authority"). When you
require an IP address block, contact your Internet Service Provider (ISP). Your ISP contacts their
local higher-level organization to reserve an IP address block:

APNIC (Asia Pacific Network Information Center)
Asia/Pacific Region

ARIN (American Registry for Internet Numbers)
Americas and Sub-Sahara Africa

LACNIC (Regional Latin-American and Caribbean IP Address Registry)
Latin America and some Caribbean Islands

RIPE NCC (Réseaux IP Européens)
Europe and Surrounding Regions
Figure 13: Bit representation of the IP address
When the first bit of an IP address is a zero, it belong to class A for example, the first octet is less
than 128.
When the first bit of an IP address is a one and the second bit is a zero, it belongs to class B for
example, the first octet is between 128 and 191.
When the first 2 bits of an IP address are a one, it belongs to class C for example, the first octet is
higher than 191.
Assigning the host address (host ID) is the responsibility of the network operator. The network
operator alone is responsible for the uniqueness of the assigned IP addresses.
2.1.2 Netmask
Routers and Gateways subdivide large networks into subnetworks. The netmask asssigns the IP
addresses of the individual devices to a particular subnetwork.
You perform subnetwork division using the netmask in much the same way as the division of the
network addresses (net id) into classes A to C.
Set the bits of the host address (host id) that represent the mask to one. Set the remaining host
address bits to zero (see the following examples).
Example of a subnet mask:
Net ID - 7 bits Host ID - 24 bits 0
I
I
I
0
I
I I I
0
I I I 0
Net ID - 14 bits
Net ID - 21 bits
Multicast Group ID - 28 bits
reserved for future use - 28 b its
Class A
Class B
Host ID - 16 bits
Host ID - 8 bit s
Class C
Class D
Class E
255.255.192.0
Decimal notation
11111111.11111111.11000000.00000000
Binary notation
Subnetwork mask bits
Class B