IP forwarding for IPv4 must not be enabled, unless the system is a router.

From Red Hat Enterprise Linux 5 Security Technical Implementation Guide

Associated with IA controls: ECSC-1

Associated with: CCI-000366

SV-37929r1_rule IP forwarding for IPv4 must not be enabled, unless the system is a router.

Vulnerability discussion

If the system is configured for IP forwarding and is not a designated router, it could be used to bypass network security by providing a path for communication not filtered by network devices.

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Fix text

Edit "/etc/sysctl.conf" and set net.ipv4.ip_forward to "0". Restart the system or run "sysctl -p" to make the change take effect.

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