Enable or allow ICMP ping incoming client request.
iptables -A INPUT -i eth0 -p icmp --icmp-type 8 -s
iptables -A OUTPUT -p icmp --icmp-type 0 -s
Allow or enable outgoing ping request.
iptables -A INPUT -i eth0 -p icmp --icmp-type 0 -s
iptables -A OUTPUT -p icmp --icmp-type 8 -s