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N00b question about iptables
https://forum.linode.com/viewtopic.php?f=19&t=9201		 Page 1 of 1
Author:  castaad [ Sat Jul 28, 2012 2:27 pm ]
Post subject:  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.

Code:
*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
Author:  castaad [ Sat Jul 28, 2012 6:22 pm ]
Post subject:  Re: N00b question about iptables
Hi,

I've managed to fix this with;

-A INPUT -p tcp -m tcp -s 192.168.0.0/16 --dport 3306 -j ACCEPT

After establishing with Linode support that NodeBalancer IP addressers are not static, but operate within the 192.168.0.0/16 range.

Thanks,
Adam.
Author:  mnordhoff [ Mon Jul 30, 2012 3:32 am ]
Post subject:  Re: N00b question about iptables
Um... 192.168.0.0/16 also covers the private IPs of every other customer in the data center, and a /17 that isn't used at all. That's a really bad idea. You should ask Linode for a more specific address range that's only used by NodeBalancers -- IIRC they used to be on 192.168.255/24 or so.
Author:  theckman [ Wed Aug 01, 2012 11:01 am ]
Post subject:  Re: N00b question about iptables
mnordhoff wrote:
Um... 192.168.0.0/16 also covers the private IPs of every other customer in the data center, and a /17 that isn't used at all. That's a really bad idea. You should ask Linode for a more specific address range that's only used by NodeBalancers -- IIRC they used to be on 192.168.255/24 or so.


Yes, NodeBalancers do use 192.168.255.0/24.
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