Festo SBO Q Series, Руководство пользователя

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A. Technical appendix
A−5
Festo P.BE−SBO−Q−EN en 0702a
Net mask Which numbers in an IP address now represent the net ID
and the host ID are defined by the specification of a so−called
net mask".
The telephone number of Festo Germany can be used as an
example to explain the IP address and the net mask:
00497113470
Which of these numbers represents the dialling code and
which represents the subscriber number becomes clear when
you also know: that the first 7 figures represent the dialling
code, the last 4 represent the subscriber number". That is the
net mask" for the telephone number above.
Net classes The net mask for IP addresses defines which bytes are used
for addressing the slave (host ID), with 0" as a position
marker. Networks belong to different net classes depending
on the number of these bytes:
Net class Net mask Explanation
A 255.0.0.0 Large network
B 255.255.0.0 Medium network
C 255.255.255.0 Small network with max.
254stations
Tab.A/1: The most important net classes with the appropriate
net masks (example)
Gateway Networks with different Net−IDs are connected to each other
via a router or gateway. If a slave in a network is to send
data to slaves in other networks, the IP address of the gate
way must be specified.