4
Industrial Ethernet networks – Basics
Network class
Manual – MOVI-C
®
CONTROLLER progressive UHX65A-M
17
4.4
Network class
The first byte of the IP address determines the network class and as such represents
the division into network address and node address:
Range of val-
ues
(byte 1 of the
IP address)
Network
class
Example: Complete
network address
Meaning
0 – 127
A
10.1.22.3
10 = Network address
1.22.3 = Node address
128 – 191
B
172.16.52.4
172.16 = Network address
52.4 = Node address
192 – 223
C
192.168.10.4
192.168.10 = Network address
4 = Node address
Node addresses that consist only of zeros or ones are not permitted. The smallest ad-
dress (all bits are zero) describes the network itself and the largest address (all bits
are 1) is reserved for the broadcast.
This rough division is not sufficient for a number of networks. The networks also use
an explicit, adjustable subnet mask.
4.5
Subnet mask
A subnet mask is used to divide the network classes into even finer sections. Like the
IP address, the subnet mask is represented by 4 decimal numbers separated by
decimal points.
Each decimal number stands for 1 byte (8 bits) of the subnet mask and can also be
represented using binary code:
Example of a subnet mask: 255.255.255.128
Byte
Decimal
Binary
1
255
11111111
2
255
11111111
3
255
11111111
4
128
10000000
The binary representation of the IP address and the subnet mask shows that in the
subnet mask, all bits of the network address are set to 1 and only the bits of the node
addresses have the value 0:
IP address: 192.168.10.129
Subnet mask: 255.255.255.128
Meaning
Bytes 1 – 4
Bytes 1 – 4
Network address
11000000
11111111
10101000
11111111
00001010
11111111
Node address
10000001
10000000
26881144/EN – 02/2022