Ask HN: Can someone help with Iptables and MySQL replication?

I have two machines. Machine 1: Front-end/Webserver (Nginx), Slave DB (IP example: slavedb.1.1.1) Machine 2: Master DB (IP example: masterdb.1.1.1) When iptables rules are removed, replication between master-slave (MySQL) works fine. I've setup the machines so they both have private IPs. When I added some generic rules, replication breaks. Below is the 'generic' rules that I used. *filter # Allows all loopback (lo0) traffic and drop all traffic to 127/8 that doesn't use lo0 -A INPUT -i lo -j ACCEPT -A INPUT ! -i lo -d 127.0.0.0/8 -j REJECT # Accepts all established inbound connections -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT # Allows all outbound traffic # You can modify this to only allow certain traffic -A OUTPUT -j ACCEPT # Allows HTTP and HTTPS connections from anywhere (the normal ports for websites) -A INPUT -p tcp --dport 80 -j ACCEPT -A INPUT -p tcp --dport 443 -j ACCEPT # Allows SSH connections # THE -dport NUMBER IS THE SAME ONE YOU SET UP IN THE SSHD_CONFIG FILE -A INPUT -p tcp -m state --state NEW --dport 30000 -j ACCEPT # Allow ping -A INPUT -p icmp -m icmp --icmp-type 8 -j ACCEPT # log iptables denied calls -A INPUT -m limit --limit 5/min -j LOG --log-prefix "iptables denied: " --log-level 7 # Reject all other inbound - default deny unless explicitly allowed policy -A INPUT -j REJECT -A FORWARD -j REJECT COMMIT Can someone provide an example of an iptables ruleset that I would use? Would I use it on both machines or only one? Thanks in advance or helping me out!