SLEM 5 must not be performing Internet Protocol version 4 (IPv4) packet forwarding unless the system is a router.

Routing protocol daemons are typically used on routers to exchange network topology information with other routers. If this software is used when not required, system network information may be unnecessarily transmitted across the network.

Verify SLEM 5 is not performing IPv4 packet forwarding, unless the system is a router with the following command:

     > sudo sysctl net.ipv4.ip_forward
     net.ipv4.ip_forward = 0

If the network parameter "ipv4.ip_forward" is not equal to "0", or nothing is returned, this is a finding.

Configure SLEM 5 to not performing IPv4 packet forwarding by running the following command as an administrator:

     > sudo sysctl -w net.ipv4.ip_forward=0

If "0" is not the system's default value, add or update the following line in "/etc/sysctl.d/99-stig.conf":

     > sudo sh -c 'echo "net.ipv4.ip_forward=0" >> /etc/sysctl.d/99-stig.conf'

     > sudo sysctl --system