Network Classes

Three different network classes are distinguished. They specify how many address bits are reserved for the Network -ID and how many for the computer number (or node number). The difference is located in the first 3 bits of the IP address.

Network-
class

Number of bits
for the Network ID

Possible number
of networks

Number of bits for
the node address

Possible number of
nodes per network

A

7

126

24

16 777 214

B

14

16 382 

16

65 536

C

21

2 097 150 

8

254

 

Note
Warning

An IP address must be unique within the entire connected network!

 

 

Note

In a communication with another Ethernet devices, the IP address set must have the same network class. Example: Your PC has address 172.16.17.55, which means that the Bus Coupler must have address 172.16.xxx.xxx (each xxx stands for a number between 0...255. The 0 is normally used for routers/switches, and should therefore be 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.