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MultiCom Firewall User’s Manual 109
Frequently Asked Questions
What is the order that data goes through the firewall?
1. Data comes into an interface as Input and is subject to Input NAT rules for
the particular interface
2. Data is subject to filtering rules* (in the Filtering Forward Panel)
3. Data is subject to routing rules
4. Data goes out an Interface as Output and is subject to Output NAT rules for
the particular interface
*data going directly to the firewall (telnet for example) use the Filtering Input
panel and data leaving directly from the firewall (syslog message for example)
uses the Filtering Output panel
How can I filter any thing but a certain address?
In the filtering source window you have the option of adding a ! before the IP
address or Port number. For instance if you selected !10.0.0.1 you are
selecting every IP address but 10.0.0.1. The same reaction occurs for ports
such as !1000–2000 means all ports except those between 1000 and 2000.
If I log a packet will it continue through the filtering rules or will it be dropped?
Logging a packet in the filtering rules table does not stop it from going
through other rules which in turn could drop, accept or use any other available
action on them.
What is a connection and how does it affect my filtering rules?
Because data packets are necessarily small they may not contain all of the
information that was requested in a data transaction (such as downloading a
web page). When the first packet is allowed through you are actually saying
that traffic related to this connection should be allowed through until its
completion.
What is the IP address of my firewall?
Devices do not have IP addresses, only their interfaces. In that sense there are
two IP addresses that will reach you firewall, the one on the LAN side and the
one on the WAN side. If you have a DMZ, Wireless, DSL or multi-PPPoE
configurations, your MultiCom can be reached by IP addresses assigned to
those interfaces.
Do routing rules take place before or after IP addresses have been translated by
NAT?
Routing takes place after IP network address translation, unless Output NAT