Title

The Red Hat Enterprise Linux operating system must not be performing packet forwarding unless the system is a router. (Cat II impact)

Discussion

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.

Check Content

Verify the system is not performing packet forwarding, unless the system is a router. # grep net.ipv4.ip_forward /etc/sysctl.conf /etc/sysctl.d/* net.ipv4.ip_forward = 0 If "net.ipv4.ip_forward" is not configured in the /etc/sysctl.conf file or in the /etc/sysctl.d/ directory, is commented out, or does not have a value of "0", this is a finding. Check that the operating system does not implement IP forwarding using the following command: # /sbin/sysctl -a | grep net.ipv4.ip_forward net.ipv4.ip_forward = 0 If IP forwarding value is "1" and the system is hosting any application, database, or web servers, this is a finding.

Fix Text

Set the system to the required kernel parameter by adding the following line to "/etc/sysctl.conf" or a configuration file in the /etc/sysctl.d/ directory (or modify the line to have the required value): net.ipv4.ip_forward = 0 Issue the following command to make the changes take effect: # sysctl --system

Additional Identifiers

Rule ID: SV-204625r603261_rule

Vulnerability ID: V-204625

Group Title: SRG-OS-000480-GPOS-00227

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.