BASH IP Tables

IPTABLES:

Allow PING ICMP

iptables -A INPUT -p icmp -j ACCEPT

Online Generator

https://www.perturb.org/content/iptables-rules.html

Docker SMTP Block IP Address

You need to insert your rule above the RETURN all rule at point # 1.

List your rules...

iptables -L DOCKER-USER --line-numbers

Chain DOCKER-USER (1 references)
num  target     prot opt source               destination     
1    RETURN     all  --  anywhere             anywhere

Then insert your rule at point # 1...

iptables --insert DOCKER-USER 1 --protocol tcp --src 31.210.20.130 --dst ip-172-20-0-2.eu-west-2.compute.internal --dport 25 --jump DROP

Then check your rules again...

iptables -L DOCKER-USER --line-numbers

Chain DOCKER-USER (1 references)
num  target     prot opt source               destination    
1    DROP       tcp  --  31.210.20.130        ip-172-20-0-2.eu-west-2.compute.internal  tcp dpt:smtp
2    RETURN     all  --  anywhere             anywhere

Done.

https://docs.docker.com/network/iptables/

Use IPTables Firewall To Block An IP Address

For a single IP address...

iptables -I INPUT -s 123.45.67.89 -j DROP

For a range of IP addresses...

iptables -I INPUT -s 123.45.67.0/24 -j DROP

Use IPTables To List A Blocked IP Address

iptables -L INPUT -v -n

iptables -S

iptables -L INPUT --line-numbers

Thanks to Cyberciti

Thanks to Cyberciti

Use IPTables To Edit / Delete A Chain Rule

List the rules of the Chain first...

iptables -L INPUT --line-numbers

...then delete the Number you want to clear...

iptables -D INPUT 4

Use IPTables To Delete ALL Rules

Thanks to Cyberciti