[iptables] Enable or allow ICMP ping incoming client request

iptables -I INPUT  -p icmp --icmp-type 8 -s 0/0 -d 0/0 -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT
iptables -I OUTPUT -p icmp --icmp-type 0 -s 0/0 -d 0/0 -m state --state ESTABLISHED,RELATED     -j ACCEPT

Reference:

• Linux Iptables allow or block ICMP ping request