Packet Filters; Packet Filters > Packet Filter Rules - Multitech RouteFinder RF850 User Manual

Packet Filters

Packet Filters > Packet Filter Rules
The Packet Filter is a key element of the RouteFinder. Packet filters are used to set firewall rules which define
what type of data traffic is allowed across the RouteFinder's firewall. There are certain System Defined Rules
that exist by default. You can specify whether particular packets are to be forwarded through the RouteFinder
system or filtered. These rules are set with the help of network/host definitions and service definitions on the
Networks & Services screen.
Prerequisites
To be able to differentiate rules, the appropriate Networks & Services > Service Groups and Networks &
Services > Network Groups must first be defined.
Show Packet Filter Rules in Popup Window
When you click Show, the screen expands to show the existing packet filter rules.
The RouteFinder's behavior is determined by the content and order of the filter rules. The filter rules are
assigned by column number (column nr). Every incoming data packet is checked, in order, as to
whether rule 1 is valid; rule 2 is valid, etc.) As soon as a correspondence is found, the procedure as
determined is carried out. You can Accept, Drop, Reject, Log the packets. When packets are rejected,
an entry in the appropriate log file occurs.
All rules are entered according to the principle: From Client - Service - To Server - Action.
When setting packet filters, the two fundamental types of security policies are:
•
All packets are allowed through – Rules Setup has to be informed explicitly what is forbidden.
•
All packets are blocked – Rules Setup needs information about which packets to let through.
Your RouteFinder default is the all packets are blocked setting, as this procedure can achieve an
inherently higher security. This means that you explicitly define which packets may pass through the
filter. All other packets are blocked and are displayed in the Filter LiveLog.
Example: Network A is contained in network B.
Rule 1 allows network A to use the SMTP service.
Rule 2 forbids network B to use SMPT.
Result: Only network A is allowed SMPT. SMPT packets from all other network B IP addresses
are not allowed to pass and are logged.
Caution: Re-sorting the rules may change how the RouteFinder operates. Be very careful when
defining the rule set. It determines the security of your RouteFinder.
If one rule applies, the subsequent ones are ignored. Therefore, the sequence is very
important. Never place a rule with the entries Any – Any – Any – Accept at the top of
your rule set, as such a setting will match all packets, and thus, cause all subsequent
rules to be ignored.
Multi-Tech Systems, Inc. RouteFinder RF850/860 User Guide (PN S000400E)
Chapter 6 – RouteFinder Software
Packet Filters > Packet Filter Rules
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