Users Guide

Setup and Administration 43
Firewall Configuration on Systems Running Supported Red Hat Enterprise Linux Operating Systems
If you enable firewall security when 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. See "Ports" for additional information.
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 opens.
2 Select Firewall Configuration using the down arrow and press <Enter>.
The
Firewall Configuration screen opens.
3 Select the Security Level by tabbing to it and pressing the spacebar. 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 Windows GUI, pressing <F1> might not provide information about firewall security
levels on newer versions of the Red Hat Enterprise Linux operating system.
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.
4 Tab to Customize and press <Enter>.
The
Firewall Configuration - Customize screen opens.
5 Select whether to open an entire network interface or just the SNMP port on all network interfaces.
a To open an entire network interface, tab to one of the Trusted Devices and press the spacebar. An
asterisk in the box to the left of the device name indicates that the entire interface will be opened.
b To open the SNMP port on all network interfaces, tab to Other ports and type snmp:udp .
6 Tab to OK and press <Enter>.
The
Firewall Configuration screen opens.