On a Linux router, packet forwarding for IPv4 has been enabled. After a reboot, the machine no
longer forwards IP packets from other hosts. The command echo 1 > /proc/sys/net/ipv4/ip_forward temporarily resolves this issue.
Which one of the following options is the best way to ensure this setting is saved across system restarts?
A.
Add echo 1 > /proc/sys/net/ipv4/ip_forward to the root user login script.
B.
Add echo 1 > /proc/sys/net/ipv4/ip_forward to any user login script.
C.
In /etc/sysctl.conf change net.ipv4.ip_forward to 1.
D.
In /etc/rc.local add net.ipv4.ip_forward = 1.
E.
In /etc/sysconfig/iptables-config add ipv4.ip_foward = 1.