Users Guide

Setup and Administration 41
Firewall Configuration on Systems Running
Supported Red Hat Enterprise Linux Operating
Systems
If you enable firewall security while installing Red Hat Enterprise Linux, the
SNMP port on all external network interfaces is closed by default. To enable
SNMP management applications such as IT Assistant to discover and retrieve
information from Server Administrator, the SNMP port on at least one external
network interface must be open. If Server Administrator detects that the
SNMP port is not open in the firewall for any external network interface, Server
Administrator displays a warning message and logs a message to the system log.
You can open the SNMP port by disabling the firewall, opening an entire
external network interface in the firewall, or opening the SNMP port for at
least one external network interface in the firewall. You can perform this
action before or after Server Administrator is started.
To open the SNMP port using one of the previously described methods,
perform the following steps:
1
At the Red Hat Enterprise Linux command prompt, type setup and
press <Enter> to start the Text Mode Setup Utility.
NOTE: This command is available only if you have performed a default
installation of the operating system.
The Choose a Tool menu appears.
2 Select Firewall Configuration using the down arrow and press <Enter>.
The
Firewall Configuration screen appears.
3 Press <Tab> to select Security Level and then press the spacebar to select
the security level you want to set. The selected Security Level is indicated
by an asterisk.
NOTE: Press <F1> for more information about the firewall security levels. The
default SNMP port number is 161. If you are using the X Window System
graphical user interface, pressing <F1> may not provide information about
firewall security levels on newer versions of Red Hat Enterprise Linux.
a
To disable the firewall, select No firewall or Disabled and go to step 7.
b To open an entire network interface or the SNMP port, select High,
Medium,
or Enabled and continue with step 4.