Funkwerk elmeg t444, Operating Instructions Manual, Page: 66 / 84

Firewall
When you use NAT, the PCs connected to the PABX are well protected against attacks from the Internet.
If you wish to have additional security you can also use the integrated package Filter Firewall. A firewall acts as a logical wall for data packets
between the Internet and the LAN which has »holes« for certain packets (firewall rules, also known as filters), allowing these packets to pass
through the wall. In the initial status the firewall is configured such that all data can pass through that are sent in the direction of the Internet.
An exception to this rule is the »Netbios filter: This filter prevents the forwarding of Netbios name queries from Wind-
ows PCs to the Internet. As the names of the Windows PCs within the LAN are not known in the Internet, it is not mea-
ningful to establish an Internet connection for forwarding the name query (this could result in considerable costs, as
these name queries occur frequently, meaning that the Internet connection would practically never be terminated).
The filters are described by rules whose configuration requires expert knowledge about the TCP/IP protocol family. The firewall of your
PABX system can be easily configured using a Filter Wizard in which you need to indicate (in plain text) whether you wish to allow defined
applications access to the Internet.
To start the Filter Wizard in the configuration item »Network filters« click the button »Filter Wizard«. The following mask is then displayed
after a warning that starting the Filter Wizard will delete all filters that have been configured up to this time:
The Filter Wizard can be restarted at any time to load a modified (edited) configuration into the PABX system. Click the button »Send confi-
guration data« to transfer and activate the filters. After the data is sent the new configuration is activated in the PABX system and any on-
going Internet connection is terminated.
The connection is re-established however as soon as a data packet must be routed to the Internet which the firewall lets pass in accordance
with its configuration.
Notes:
Note that when you click the button Send, the entire configuration for the PABX system will be overwritten. It is strongly recommended to
read out the configuration for the PABX system and storing it in a file prior to changing the filter configuration.
We recommend following the instructions given by the Filter Wizard, unless you establish that one of the applications you are using can not
set up a connection to the Internet. In this case, please check whether the Filter Wizard has a corresponding filter available. Elmeg regularly
generates an updated database for the Filter Wizard, which is available at the www. elmeg. de Web site.
Please note that all filters that are generated with the Filter Wizard are based on packets being discarded, with the exception of those for
which an appropriate rule exists. The more filters you configure for the PABX system, the more computing time is required for processing of
these filters. This could slightly reduce the maximum achievable data throughput rate for the PABX system in some cases.
Information on manual configuration of firewall filter rules is given in the online Help function and in the documentation located on the CD.
Costs for Internet connections
The PABX can store up to 500 call data records. This data is not lost in the event of a loss of power.
Description of the router functions
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