Firewall settings in Linux

To modify the firewall configuration, you need to modify the/etc/sysconfig/iptables file. if you want to open a port, add one in it. -ARH-Firewall-1-INPUT-mstate -- stateNEW-mtcp-ptcp -- the dport1521-jACCEPT is ready, where 1521 is the port number to be opened, and then restart the firewall server of linux to modify the firewall configuration to be modified/etc/sysconfig/ IptablesIf you want to open this file, add a port in it. -A RH-Firewall-1-INPUT-m state -- state NEW-m tcp-p tcp -- dport 1521-j ACCEPT
1521 indicates the port number to be opened, and then restart the firewall service in linux.
Command to stop/start the firewall service:
Run
Service iptables stop -- stop
Service iptables start -- start
(The service Command is located in/sbin)
Firewall rules can be activated only when the iptables service is running. To manually start the service, run the following command:
/Sbin rvice iptables restart
To ensure that it is started during system boot, run the following command:
/Sbin/chkconfig -- level 345 iptables on
The ipchains service cannot run with the iptables service at the same time. To disable the ipchains service, run the following command:
/Sbin/chkconfig -- level 345 ipchains off