Why is 'ip_forward' enabled by default upon boot in Red Hat Enterprise Linux?

Issue

• Upon boot, the output of /proc/sys/net/ipv4/ip_forward as well as sysctl net.ipv4.ip_forward shows ip_forward as enabled:

  $ cat /proc/sys/net/ipv4/ip_forward 
  1
  $ sysctl net.ipv4.ip_forward
  net.ipv4.ip_forward = 1
  

  • However, /etc/sysctl.conf has the parameter disabled by default:

    $ grep ip_forward /etc/sysctl.conf 
    net.ipv4.ip_forward = 0
    

• Why can't the kernel parameter net.ipv4.ip_forward = 0 be disabled permanently?

• Even if net.ipv4.ip_forward = 0 is set in /etc/sysctl.conf, ip forwarding does not get disabled after reboot