Operating Manual
Page 42 / 116
Copyright © REA Elektronik
REA ScanCheck 3n
V 1.2.0 24/02/2020
REA
VERIFIER
If the check is placed at “Device network setting”, the setting can be changed.
DHCP can be turned on or off. If DHCP is off, the desired setting can be entered in the IP address,
IP mask and gateway field
Operation with automatic address assignment is recommended; if, on the other hand, fixed
addresses are needed, the DHCP server must ensure that devices with defined MAC address are
always assigned the same IP address.
3.10 General information about network addresses
The abbreviation TCP/IP stands for
T
ransmission
C
ontrol
P
rotocol/
I
nternet
P
rotocol. More detailed
information can be fou
nd under the entry TCP/IP in the “Wikipedia” Internet encyclopaedia
(
http://de.wikipedia.org/wiki/TCP/IP
)
An IP address (version 4) consists of four number blocks, each of which can be given the value
“255” at a maximum. The first three number blocks of the IP address often have the same values
as the PC being used. With the fourth number block, the respective device identifies itself with an
individual group of numbers.
Good to know: Each IP address is only allowed to occur once in the network
If that would not be so, several different devices would be addressed under one number (=
address). Then a so-called IP address conflict would come into being.
The DHCP server must prevent such errors.
The “subnet mask” also consists of 4 blocks with values between “0” and “255”. A common variant
is 255.255.255.0. In larger organisations, there might be a 255.255.240.0, for instance. The subnet
mask determines how many different IP addresses can be used in a network area. When number
blocks in the IP address of the device are different in those places that have the value 255 in the IP
mask, then these devices are assigned to different networks, so communication among them is not
possible.
3.11 Firewall
A firewall is always enabled on properly configured PCs. The firewall is designed to prevent
malicious programs from infiltrating the PC via the network connection or that data of the PC is
mined. When the network communication with the REA ScanCheck 3n begins, it is not yet known to
the firewall program. Depending on the setting, it will prevent the communication or ask whether the
communication is allowed. It is necessary to ensure that the firewall does not block communication
between the PC and REA ScanCheck 3n.
In a point-to-point connection in which the PC is never connected with a network or the Internet, the
firewall might always be switched off. In companies with a high level of security requirements, the
firewall will prevent network operation without any indication or error message. In such cases, the
IT administration must configure the firewall correctly.
