5
Startup with PROFINET IO
Industrial Ethernet networks
Manual – MOVI-C
®
CONTROLLER advanced with PROFINET IO Fieldbus Interface
48
5.1.4
Network class
The first byte of the IP address determines the network class and as such represents
the division into network addresses and node addresses:
Range of val-
ues
(Byte 1 of 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.
5.1.5
Subnetwork 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:
Exemplary 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
Bytes 1 – 4
Bytes 1 – 4
Network address
11000000
11111111
10101000
11111111
00001010
11111111
Node address
10000001
10000000
24777730/EN – 01/2018
