N00b question about iptables

Hi,

I have 2 Linodes (App1 and App2) running a web application behind a NodeBalancer. The two application servers connect to a database server (DB1) though a 2nd NodeBalancer. Both application servers were able to access the database server through the NodeBalancer until I implimented iptables to secure the database server (DB1).

I've included my iptables config below - please could someone help and advise a suitable rule? Would really appreciate your help.

In an attempt to get things working I implemented the "# Allow connections from other Linodes" section with all the Linode IP's but this doesn't seem to have worked.

*filter

# Allow 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

# Accept all established inbound connections
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

# Allow all outbound traffic - you can modify this to only allow certain traffic
-A OUTPUT -j ACCEPT

# Allow SSH connections
-A INPUT -p tcp -m state --state NEW --dport 22 -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

# Allow connections from other Linodes
# External Ip's
-A INPUT -s IPADDRESSHERE -j ACCEPT
-A INPUT -s IPADDRESSHERE -j ACCEPT
-A INPUT -s IPADDRESSHERE -j ACCEPT
-A INPUT -s IPADDRESSHERE -j ACCEPT
# Internal Ip's
-A INPUT -s IPADDRESSHERE -j ACCEPT
-A INPUT -s IPADDRESSHERE -j ACCEPT
-A INPUT -s IPADDRESSHERE -j ACCEPT
-A INPUT -s IPADDRESSHERE -j ACCEPT
# Balancers
-A INPUT -s IPADDRESSHERE -j ACCEPT
-A INPUT -s IPADDRESSHERE -j ACCEPT
# External Ip's
-A OUTPUT -s IPADDRESSHERE -j ACCEPT
-A OUTPUT -s IPADDRESSHERE -j ACCEPT
-A OUTPUT -s IPADDRESSHERE -j ACCEPT
-A OUTPUT -s IPADDRESSHERE -j ACCEPT
# Internal Ip's
-A OUTPUT -s IPADDRESSHERE -j ACCEPT
-A OUTPUT -s IPADDRESSHERE -j ACCEPT
-A OUTPUT -s IPADDRESSHERE -j ACCEPT
-A OUTPUT -s IPADDRESSHERE -j ACCEPT
# Balancers
-A OUTPUT -s IPADDRESSHERE -j ACCEPT
-A OUTPUT -s IPADDRESSHERE -j ACCEPT

# Reject all other inbound - default deny unless explicitly allowed policy
-A INPUT -j REJECT
-A FORWARD -j REJECT

COMMIT