Hirschmann MACH 4000 Series, User Manual

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Entering the IP parameters
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2.1 Basics IP parameter
Basic - L3P
Release 3.1 06/07
Fig. 7: Bit representation of the IP address
All IP addresses belong to class A when their first bit is a zero, i.e. the first
decimal number is less than 128.
The IP address belongs to class B if the first bit is a one and the second bit
is a zero, i.e. the first decimal number is between 128 and 191.
The IP address belongs to class C if the first two bits are a one, i.e. the first
decimal number is higher than 191.
Assigning the host address (host id) is the responsibility of the network
operator. He alone is responsible for the uniqueness of the IP addresses
he assigns.
2.1.2 Network mask
Routers and gateways subdivide large networks into subnetworks. The net-
work mask assigns the IP addresses of the individual devices to a particular
subnetwork.
The division into subnetworks with the aid of the network mask is performed
in much the same way as the division of the network addresses into classes
A to C (net id).
In the part of the host address (host id) representing the mask, the bits are
set to one. The remaining bits of the host address in the network mask are
set to zero (see the following examples).
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
Klasse A
Klasse B
Host ID - 16 bits
Host ID - 8 bit s
Klasse C
Klasse D
Klasse E