System Introduction
2–22
1070 072 262-101 (01.09) GB
2.4.1
Subnetwork Mask
A subnetwork mask will be linked additionally to the IP address via which all
communicating components in a network can be reached. It looks like an IP
address, e.g. 255.255.0.0 could be a possible subnetwork mask.
The subnetwork mask must be equal for all stations in a network in order for
them to know that they belong to the same network. The subnetwork mask
determines the possible size of a network. I.e., that so-called subnetworks
can be defined.
The CL550 operates two independent Ethernet interfaces in a controller:
Frontside and Backside, please refer to page 2–21. In order to distinguish
the physical access to the components, the two interfaces must be located in
different subnetworks. The subnetwork mask, though, is identical for both
interfaces.
.
In order to make unambiguous addressing possible, it is important
that the subnetwork mask will be adjusted to the IP addresses of the
front- and the backside.
The subnetwork address for the frontside results from
D
the IP address of the frontside and
D
an AND operation with the subnetwork mask.
The subnetwork address for the backside results from
D
the IP address of the backside and
D
an AND operation with the subnetwork mask.
