ADD/DELETE/MODIFY IPTABLES firewall RULE in DD-WRT ROUTER

For example I am allowing ping request to DD-WRT router. Below iptables commands can be used on any Linux Operating System.

We can't to ping dd-wrt router's public or private ip because of iptables firewall rule. By default iptables drop ICMP request. If you want to allow ping then we need to allow ping in dd-wrt router.For allowing ping to ip of DD-WRT Router), we need to run iptables rule because I did not find any option to allow ping to lan ip.
Some useful iptables commands
# The default behaviour => accept connections
iptables -P INPUT ACCEPT
iptables -P OUTPUT ACCEPT
iptables -P FORWARD ACCEPT
# Allow ESTABLISHED and RELATED incoming connection
iptables -A INPUT -i eth0 -m state --state ESTABLISHED,RELATED -j ACCEPT
# Allow loopback traffic
iptables -A INPUT -i lo -j ACCEPT
#Allow ICMP
iptables -A INPUT -p icmp -i eth0 -j ACCEPT
#Do not allow ICMP
iptables -A INPUT -p icmp -i eth0 -j DROP

# Below command will show list of INPUT rules with line numbers

iptables -L INPUT --line-numbers
Chain INPUT (policy ACCEPT)
num target prot opt source destination
1 ACCEPT udp -- anywhere anywhere udp dpt:12345
2 ACCEPT 0 -- anywhere anywhere state RELATED,ESTABLISHED
3 DROP udp -- anywhere anywhere udp dpt:route
4 DROP udp -- anywhere anywhere udp dpt:route
5 ACCEPT udp -- anywhere anywhere udp dpt:route
6 logaccept tcp -- anywhere DD-WRT tcp dpt:www
7 logaccept tcp -- anywhere DD-WRT tcp dpt:ssh
8 DROP icmp -- anywhere anywhere
9 DROP igmp -- anywhere anywhere
10 ACCEPT 0 -- anywhere anywhere state NEW
11 logaccept 0 -- anywhere anywhere state NEW
12 DROP 0 -- anywhere anywhere
#Below command will replace rule no 8 in iptables firewall and it will allow icmp request
iptables -R INPUT 8 -p icmp --icmp-type echo-request -j ACCEPT
-R = will repalce the iptables rule
8 = Rule no 8
#Disable iptables rule number wise
iptables -R INPUT 8 -p icmp --icmp-type echo-request -j DROP
#Delete iptables rule number wise
iptables -D INPUT 8
-D=Delete rule
8= Rule no 8