Editing Talk:Using NAT for container with private IPs

== ip_conntrack_disable_ve0=1 ==
I was stumbling a lot with the configuration where allowing access to a service from outside, because I assumed that after adding the iptables DNAT rule, I could test the rule from the hardware node. The rule only works for packets send from outside.

I added some text about it now, but maybe someone could rephrase it more nicely.
----

<pre>For OpenVZ kernels later than 2.6.8, connection tracking 
for VE0 is enabled by default. However, make sure there is no line like 

options ip_conntrack ip_conntrack_disable_ve0=1
</pre>

It seems to me that here must be =0 ??? Or not?

[[User:Shaplov|Shaplov]] 10:27, 23 June 2007 (EDT)

: See, it tells there should be '''no''' line that '''disables''' conntrack. --[[User:Kir|Kir]] 14:09, 8 April 2009 (UTC)

== How to supply public IPs? ==

"Usually you supply public IP addresses to your containers"? How? [[User:Guaka|Guaka]] 14:03, 8 April 2009 (UTC)
: Well, by running <code>vzctl set $CTID --ipadd a.b.c.d --save</code> command (where a.b.c.d is a public IP address) --[[User:Kir|Kir]] 14:06, 8 April 2009 (UTC)

== For nuts like me on CentOs6 ==
After several hours I found my config minimal with : gateway 192.168.1.1, host(centos6) 192.168.1.101 and containers 192.168.2.1/23
Probably, it's not clean but it works :

Clean in the host the iptables with system-config-firewall-tui where you enable firewall and click on OK :
 # system-config-firewall-tui

You have now in /etc/sysconfig/iptables :
<pre># Firewall configuration written by system-config-firewall
# Manual customization of this file is not recommended.
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
-A INPUT -p icmp -j ACCEPT
-A INPUT -i lo -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT
-A INPUT -j REJECT --reject-with icmp-host-prohibited
-A FORWARD -j REJECT --reject-with icmp-host-prohibited
COMMIT
</pre>

After enable ip foward in the file "/etc/sysctl.conf" :
 net.ipv4.ip_forward = 1

You can test :
 vzctl start 3 
 vzctl enter 3
 ping 192.168.1.101 => OK
 ping 192.168.1.1 => Destination Host Prohibited

So after you execute the lines :
 iptables -t nat -A POSTROUTING -j SNAT --to-source 192.168.1.101
 iptables -A FORWARD -s 192.168.2.1/24 -j ACCEPT
 iptables -A FORWARD -d 192.168.2.1/24 -j ACCEPT
 service iptables save

You have now the file /etc/sysconfig/iptables :
<pre># Generated by iptables-save v1.4.7 on Fri Jul 20 14:31:56 2012
*nat
:PREROUTING ACCEPT [10:683]
:POSTROUTING ACCEPT [0:0]
:OUTPUT ACCEPT [30:1720]
-A POSTROUTING -j SNAT --to-source 192.168.1.101
COMMIT
# Completed on Fri Jul 20 14:31:56 2012
# Generated by iptables-save v1.4.7 on Fri Jul 20 14:31:56 2012
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [400:53438]
-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -p icmp -j ACCEPT
-A INPUT -i lo -j ACCEPT
-A INPUT -p tcp -m state --state NEW -m tcp --dport 22 -j ACCEPT
-A INPUT -j REJECT --reject-with icmp-host-prohibited
-A FORWARD -j REJECT --reject-with icmp-host-prohibited
-A FORWARD -s 192.168.2.0/24 -j ACCEPT
-A FORWARD -d 192.168.2.0/24 -j ACCEPT
COMMIT
# Completed on Fri Jul 20 14:31:56 2012
</pre>

If you test again it's wrong :
 vzctl enter 3
 ping 192.168.1.1 => Destination Host Prohibited

Move the lines with icmp-host-prohibited at the end of file :
<pre># Generated by iptables-save v1.4.7 on Fri Jul 20 14:31:56 2012
*nat
:PREROUTING ACCEPT [10:683]
:POSTROUTING ACCEPT [0:0]
:OUTPUT ACCEPT [30:1720]
-A POSTROUTING -j SNAT --to-source 192.168.1.101
COMMIT
# Completed on Fri Jul 20 14:31:56 2012
# Generated by iptables-save v1.4.7 on Fri Jul 20 14:31:56 2012
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [400:53438]
-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -p icmp -j ACCEPT
-A INPUT -i lo -j ACCEPT
-A INPUT -p tcp -m state --state NEW -m tcp --dport 22 -j ACCEPT
-A FORWARD -s 192.168.2.0/23 -j ACCEPT
-A FORWARD -d 192.168.2.0/23 -j ACCEPT
-A INPUT -j REJECT --reject-with icmp-host-prohibited
-A FORWARD -j REJECT --reject-with icmp-host-prohibited
COMMIT
# Completed on Fri Jul 20 14:31:56 2012
</pre>

After restart service :
 service iptables restart

If you test again it's ok :
 vzctl enter 3
 ping 192.168.1.1 => ok

Config after /etc/resolv.conf :
 # Generated by NetworkManager
 domain home
 search home
 nameserver 192.168.1.1

Enjoy !
@@ Line 130: / Line 130: @@
 Enjoy !
-== Note pour NAT d'IP privée (FR) ==
-(cyrille le 18/08/2012)
-Après quelques moments de galères avec la ligne:
-  $iptables -t nat -A POSTROUTING -s $the_private_network -o eth0 -j SNAT --to $the_public_ip
-En fait il faut mettre l'interface vmbr0 au lieu de eth0.
-  $iptables -t nat -A POSTROUTING -s $the_private_network -o vmbr0 -j SNAT --to $the_public_ip
-Et encore mieux, ne pas mettre d'interface:
-  $iptables -t nat -A POSTROUTING -s $the_private_network -j SNAT --to $the_public_ip