Examples Of Filters That Perform Common Functions; Building A Firewall With Passpacket Filters; A Filter That Will Block All Except Specific Ftp Packets; A Filter That Will Bring Up A Connection When It Detects Ip Packets - Digi PortServer II User Manual

Examples of filters that perform common functions

Building a firewall with passpacket filters

Filters can be defined to selectively pass or block IP packets based on:
• Inbound or outbound packet IP address
• Source or destination IP address
• TCP/UDP port
• Protocol
You can configure passpacket filters using any or all of these criteria to build a secu-
rity firewall between the Internet and a local network.
For example, if your WWW server has an IP address of 199.86.8.33, configure a filter
similar to that shown below and call it filter 1:
s1= 199.86.8.33 //Match if IP source or destination address is
You can then enter a command similar to the following:
set user name=webconnection network PassPacket=filter1
This will pass packets that match the WWW server's IP address and block all others.

A filter that will block all except specific ftp packets

The following filter blocks all incoming ftp packets except those to host 199.86.8.22
and allows other packets. You must define ftp in the Service Table, using the set
service command:
s1=ftp/syn/recv/dst/199.86.8.22//allow incoming ftp with dest
s2=!ftp/syn/recv

A filter that will bring up a connection when it detects IP packets

The following filter brings up a connection when it detects telnet or rlogin IP packets:
s1=telnet
s2=rlogin
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199.86.8.33
//allow all other packets except
Configuring WAN Connections
addr of 199.86.8.22
incoming ftp
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