Operating Instructions and Installation Instructions

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Glossary
services. This is also a way of preventing any Trojans (ma-
licious applications opening backdoors on a computer)
that may have infected your computer from receiving data
on ports it created as means of accessing your computer
for potentially damaging activities. A firewall blocks most
atypical port numbers not required for normal operation of
an application and offers specialized users the opportuni-
ty to forward specified ports.
port forwarding With port forwarding it is possible to specify ports that will
allow all incoming or outgoing data packets to pass
through a router or firewall.
If a computer from the local network offers server services,
for instance, the settings of a router using NAT or IP mas-
querading must forward the port used by the server ser-
vice for access to incoming data packets and thus keep it
open permanently. The private IP address of the given
computer must be saved as the destination address for all
of the packets arriving at the port.
Typical server applications which require port forwarding
are FTP and Web servers. To allow access to a computer via
remote management software like Symantec pcAnywhere
or Microsoft’s Remote Desktop, or even use of a file-shar-
ing program like eMule, the required ports must be re-
leased for port forwarding. Port forwarding settings for the
most important application cases are quite simple as long
as the settings of the router or the firewall already contain
rules with a corresponding preconfiguration.
private IP
address
Private IP addresses are used for computers and other
network devices within local IP networks.
Since many local IP networks are not connected to the In-
ternet except via single computers or routers (gateway),
certain address ranges are excluded from the publicly
available IP addresses so that they are available for as-
signment in local IP networks. An IP address may only be
assigned once within the local network. A private IP ad-
dress may exist in any number of other local networks.