The ip_local_port_range parameters

Securing and Optimizing Linux: RedHat Edition -A Hands on Guide
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# 6.7. The ip_local_port_range parameters

The `/proc/sys/net/ipv4/ip_local_port_range` defines the local port range that is used by TCP and UDP traffic to choose the local port. You will see in the parameters of this file two numbers: The first number is the first local port allowed for TCP and UDP traffic on the server, the second is the last local port number. For high-usage systems you may change its default parameters to 32768-61000 -first-last.

The default setup for the ip_local_port_range parameters under Red Hat Linux is: `"1024 4999"`

To change the values of ip_local_port_range, type the following command on your terminal:

                [root@deep] /# echo "32768 61000" >/proc/sys/net/ipv4/ip_local_port_range

Add the above commands to the `/etc/rc.d/rc.local` script file and you'll not have to type it again the next time you reboot your system.

Edit the `/etc/sysctl.conf` file and add the following line:

                # Allowed local port range
                net.ipv4.ip_local_port_range = 32768 61000

You must restart your network for the change to take effect. The command to manually restart the network is the following:

                [root@deep] /# /etc/rc.d/init.d/network restart

`Setting network parameters [ OK ] Bringing up interface lo [ OK ] Bringing up interface eth0 [ OK ] Bringing up interface eth1 [ OK ]`

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