Product specifications

Efficient Networks
®
Router family
Technical Reference Guide
Chapter 5: System Security
Efficient Networks
®
Page 5-27
-> remote ipfilter append input accept -p tcp -dp 23 -da
10.0.1.1 internet
-> remote ipfilter append input drop -p tcp -dp 23 internet
The filter order is important; packets are compared to filters in the order that the filters
appear in the filter list. Any Telnet packet that doesn’t match the first filter is dropped
by the second filter. Thus, command order is important because each of these
commands appends its filter to the end of the list.
Built-in Firewall Filters
Although IP filtering offers great flexibility and control, creating the required series of
commands may appear complex to a casual user. Therefore, four sets of firewall
filters are resident in the flash memory of factory-built routers.
The four sets of filters offer four levels of security: maximum, medium, minimum, and
none. You can select and install any of these filter sets from the Set Firewall page of
the Web graphic interface.
The four filter sets are also provided as script files in the samples directory on the
Documentation CD. The file names are maxsec.txt (maximum security), medsec.txt
(medium security), minsec.txt (minimum security) and nosec.txt (no filters). To
execute one of these files from the CLI, first copy the file to the router and then use
the execute command. For example, to execute the medsec.txt file for medium
security, enter:
execute medsec.txt
Before executing any script file, you should check its content. Three of the filter sets
are listed at the end of this IP Filtering section (“Example 3: Maximum Security
Firewall” on page 5-27, “Example 4: Medium Security Firewall” on page 5-29, and
“Example 5: Minimum Security Firewall” on page 5-30). Be sure to edit the file to fit
your specific configuration and seek expert help if you are not familiar with security.
Example 3: Maximum Security Firewall
The following lists the filters installed when you request maximum security via the
graphic interface.
# For DSL routers
# Allow protocols: HTTP, FTP, DNS, L2TP
# Flush all existing filters
remote ipfilter flush input internet
remote ipfilter flush output internet
remote ipfilter flush transmit internet
remote ipfilter flush receive internet