IP forwarding & prevent ot reply of ping----

[root@localhost named]    vim /etc/sysctl.conf

Just enable IP forwarding here by "1" /against "0" 1 for enable 0 for disable.

[root@localhost named]    sysctl -p

Ping reply prevent-------- 

[root@localhost named]    cat /proc/sys/net/icmp_echo_ignore_all (to see the status)
[root@localhost named]    echo 1 > /proc/sys/net/icmp_echo_ignore_all ( to prevent )
[root@localhost named]    echo 0 > /proc/sys/net/icmp_echo_ignore_all (to enable)
[root@localhost named]    vim /etc/sysctl.conf

Just enable this line --net.ipv4.icmp_echo_ignore_all=1