Security Functions; Firewall - Siemens SIMATIC NET SCALANCE S615 Configuration Manual

Technical basics

2.5 Security functions

2.5 Security functions
2.5.1

Firewall

The security functions of the device include a stateful inspection firewall. This is a method of
packet filtering or packet checking. The IP packets are checked based on firewall rules in
which the following is specified:
● The permitted protocols
● IP addresses and ports of the permitted sources
● IP addresses and ports of the permitted destinations
If an IP packet fits the specified parameters, it is allowed to pass through the firewall. The
rules also specify what is done with IP packets that are not allowed to pass through the
firewall.
Simple packet filter techniques require two firewall rules per connection.
● One rule for the query direction from the source to the destination.
● A second rule for the response direction from the destination to the source
Stateful inspection firewall
With a stateful inspection firewall, on the other hand, you only need to specify one firewall
rule for the query direction from the source to the destination. The second rule is added
implicitly. The packet filter recognizes when, for example, computer "A" is communicating
with computer "B" and only then does it allow replies. A query by computer "B" is therefore
not possible without a prior request by computer "A".
You configure the firewall in "Security > Firewall (Page 152)".
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SCALANCE S615 Web Based Management
Configuration Manual, 05/2015, C79000-G8976-C388-02