여기 숨어 있었군요.
 [root@localhost root]# cat /etc/sysctl.conf
# Disables packet forwarding
<font color="blue">net.ipv4.ip_forward = 0</font>
# Enables source route verification
net.ipv4.conf.default.rp_filter = 1
# Disables the magic-sysrq key
kernel.sysrq = 0--5 /|/ O B !