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V-221889

CAT II (Medium)

The Oracle Linux operating system must not be performing packet forwarding unless the system is a router.

Rule ID

SV-221889r991589_rule

STIG

Oracle Linux 7 Security Technical Implementation Guide

Version

V3R5

CCIs

CCI-000366

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 -r net.ipv4.ip_forward /run/sysctl.d/* /etc/sysctl.d/* /usr/local/lib/sysctl.d/* /usr/lib/sysctl.d/* /lib/sysctl.d/* /etc/sysctl.conf 2> /dev/null
     net.ipv4.ip_forward = 0

If "net.ipv4.ip_forward" is not configured in the /etc/sysctl.conf file or in any of the other sysctl.d directories, 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.

If conflicting results are returned, 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