Network Classes; Fig. 13 Network Classes - Beckhoff BK9053 Documentation

4.3

Network classes

Three different network classes are distinguished. They determine how many address bits are reserved for
the network ID and how many for the node number (e.g. for PCs or Bus Couplers). The difference is located
in the first three bits of the IP address.
Network Number of bits for
class the network ID
A 7
B 14
C 21
Unique IP address
An IP address must be unique within the entire connected network!
Fig. 13: Network classes
Identical network class
In a communication with another Ethernet devices, the IP address set must have the same network
class. Sample: Your PC has the address 172.16.17.55, which means the coupler must have the ad-
dress 172.16.xxx.xxx (xxx stands for a number between 0 and 255. 0 is usually used by the router/
switch and should therefore remain reserved).
In order to see the PC's own address, the command ipconfig can be entered into a DOS window under
Windows NT/2000/XP.
BK9053, BK9103
Enables no. of No. of bits for the
networks node address
126 24
16 382 16
2 097 150 8
Version: 2.3.0
Parameterization and commissioning
Enables no. of nodes per
network
16 777 214
65 536
254
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