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
Run the following commands to restore the default parameters and set the active kernel parameters:
# grep -Els '^s*net.ipv4.ip_forwards*=s*1' /etc/sysctl.conf /etc/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /run/sysctl.d/*.conf | while read filename; do sed -ri 's/^s*(net.ipv4.ip_forwards*)(=)(s*S+b).*$/# *REMOVED* 1/' $filename; done; sysctl -w net.ipv4.ip_forward=0; sysctl -w net.ipv4.route.flush=1
# grep -Els '^s*net.ipv6.conf.all.forwardings*=s*1' /etc/sysctl.conf /etc/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /run/sysctl.d/*.conf | while read filename; do sed -ri 's/^s*(net.ipv6.conf.all.forwardings*)(=)(s*S+b).*$/# *REMOVED* 1/' $filename; done; sysctl -w net.ipv6.conf.all.forwarding=0; sysctl -w net.ipv6.route.flush=1
Item Details
Category: CONFIGURATION MANAGEMENT, SYSTEM AND SERVICES ACQUISITION
References: 800-53|CM-2, 800-53|CM-6, 800-53|CM-7, 800-53|CM-7(1), 800-53|CM-9, 800-53|SA-3, 800-53|SA-8, 800-53|SA-10, CSCv7|5.1, Rule-ID|SV-204625r603261_rule
Control ID: 268469bf954c691f142514b7b63ba242ac94a2f39fd4b1595ab722b6d98c9f71