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

From Oracle Linux 5 Security Technical Implementation Guide

Associated with: CCI-000366

SV-64113r1_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.

Check content

Check if the system is configured for IPv4 forwarding. If the system is a VM host and acts as a router solely for the benefits of its client systems, then this rule is not applicable. Procedure: # cat /proc/sys/net/ipv4/ip_forward If the value is set to "1", IPv4 forwarding is enabled this is a finding.

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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