Red Hat Enterprise Linux 5 Administration Unleashed

Enabling the Default Firewall 503As shown in Figure 24.1, there are two tabs in the application: Firewall Options andSELinux. The Firewall Options tab is for enabling or disabling the default firewall.24FIGURE 24.1Enabling the Security LevelStart by selecting Enabled or Disabled from the Firewall pull-down menu. If you chooseDisabled, a security level is not implemented and your system will accept connections toall ports with services running on them unless SELinux, custom IPTables rules, or othersecurity measures have been enabled instead.Selecting Enabled rejects all connections to all port except the ones selected from theTrusted services list or added to the Other ports list. Notice that SSH is selected bydefault. The following trusted services can be selected so their default ports acceptconnections:. FTP. Mail (SMTP). NFS4. SSH. Samba. Secure WWW (HTTPS). Telnet. WWW (HTTP)To accept connections to additional ports, click the arrow beside Other ports to displaythe input box. For each port to add, click Add. A dialog window as shown in Figure 24.2appears prompting for a port number and the protocol (tcp or udp). Click OK to add it tothe port list.