3.2.1 Ensure IP forwarding is disabled

Information

The net.ipv4.ip_forward and net.ipv6.conf.all.forwarding flags are used to tell the system whether it can forward packets or not.

Setting the flags to 0 ensures that a system with multiple interfaces (for example, a hard proxy), will never be able to forward packets, and therefore, never serve as a router.

Solution

Set the following parameter in /etc/sysctl.conf or a /etc/sysctl.d/* file:

Example:

# printf "
net.ipv4.ip_forward = 0
" >> /etc/sysctl.d/60-netipv4_sysctl.conf

Run the following command to set the active kernel parameters:

# {
sysctl -w net.ipv4.ip_forward=0
sysctl -w net.ipv4.route.flush=1
}

IF IPv6 is enabled on the system:

Set the following parameter in /etc/sysctl.conf or a /etc/sysctl.d/* file:

Example:

# printf "
net.ipv6.conf.all.forwarding = 0
" >> /etc/sysctl.d/60-netipv6_sysctl.conf

Run the following command to set the active kernel parameters:

# {
sysctl -w net.ipv6.conf.all.forwarding=0
sysctl -w net.ipv6.route.flush=1
}

See Also

https://workbench.cisecurity.org/files/3796

Item Details

Category: CONFIGURATION MANAGEMENT

References: 800-53|CM-6, 800-53|CM-7, CSCv7|9.2

Plugin: Unix

Control ID: 5235af724781285bfccc609ba028aab26bec03d138a1e7e50a294cfc33230438