3.1.1 Ensure IP forwarding is disabled - sysctl

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.

Rationale:

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:

net.ipv4.ip_forward = 0
net.ipv6.conf.all.forwarding = 0

Run the following commands to set the active kernel parameters:
# sysctl -w net.ipv4.ip_forward=0
# sysctl -w net.ipv6.conf.all.forwarding=0
# sysctl -w net.ipv4.route.flush=1
# sysctl -w net.ipv6.route.flush=1

See Also

https://workbench.cisecurity.org/files/2449

Item Details

Category: CONFIGURATION MANAGEMENT

References: 800-53|CM-6, CSCv6|9.2, CSCv7|5.1

Plugin: Unix

Control ID: 977eb52e1b7e11910dea6018d2bbf4e546bb7d1125aff8cbb842389fe81482b5