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Need basic help with OpehVZ host iptables
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Need basic help with OpehVZ host iptables

aFriendaFriend Member

I use the following iptables setting on my dedicated server. If I install the OpenVZ kernel, and run the same tables below for host machine, the host machine can no longer resolve dns.

I am trying to run 1 host with 2 openvz containers (each with their own ip address) for private use. I want the host and containers to have their own ip tables. Your help is appreciated.

iptables -F

Allow all loopback (lo0) traffic and drop all traffic to 127/8 that doesn't use lo0

iptables -A INPUT -i lo -j ACCEPT
iptables -A INPUT -d -j REJECT

Accept all established inbound connections

iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

Allow all outbound traffic - you can modify this to only allow certain traffic

iptables -A OUTPUT -j ACCEPT

Allow HTTP and HTTPS connections from anywhere (the normal ports for websites and SSL).

iptables -A INPUT -p tcp --dport 80 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j ACCEPT

Allow SSH connections

iptables -A INPUT -p tcp --dport 22 -j ACCEPT

add some custom ports that need to be opened

iptables -A INPUT -p tcp --dport 17711 -j ACCEPT
iptables -A INPUT -p tcp --dport 17712 -j ACCEPT

Allow ping

iptables -A INPUT -p icmp -m icmp --icmp-type 8 -j ACCEPT

Log iptables denied calls

iptables -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

with the openvz kernel, the following line blocks all outbound traffic from host

iptables -A INPUT -j REJECT
iptables -A FORWARD -j REJECT

ONLY on OpenVZ Head Node This allows access to OpenVZ Containers

iptables -F FORWARD

echo "*** outputting the iptables settings before restart "
iptables -L -n
iptables-save | tee /etc/sysconfig/iptables

echo "*** restarting iptables "
service iptables restart

echo "*** outputting the iptables settings after restart "
iptables -L -n


  • edited July 2014


    It's looks like this feature/bug if you really need connection tracking on CT0 (hardware node).

    I can copy main part about this issue:

    Due to conntrack impact on venet performance, conntrack need to be disabled
    on the host system (it will still work for containers).

    Adding the following option to /etc/modprobe.d/openvz.conf

       options nf_conntrack ip_conntrack_disable_ve0=1

    This change will take effect only after the next reboot.

    NOTE: IF YOU NEED conntrack functionality, edit $file NOW,
    changing =1 to =0. DO NOT REMOVE the line, or it will be re-added!

    Thanked by 1aFriend

    We offer affordable DDoS detection software: FastNetMon

  • After this fixes you should reboot your node.

    We offer affordable DDoS detection software: FastNetMon

  • Thanks pavel. I will try this soon once I have a chance to bring the dedi down.

  • You could try do this without reboot. You can do /etc/init.d/vz stop, all CT will be suspended. After this you should rmmod all iptables modules from lsmod and then start nf_conntrack again with fixed config: modprobe nf_conntrack.

    After this all be fine.

    We offer affordable DDoS detection software: FastNetMon

  • aFriendaFriend Member
    edited July 2014

    I believe these instructions worked for me! Thx Pavel! I believe I just did a machine reboot - I didnt try without reboot.

  • Welcome :)

    Thanked by 1csofts

    We offer affordable DDoS detection software: FastNetMon

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