How to change netfilter parameters?

As of version 4.9.0, VMmanager automatically changes the settings of the netfilter built-in firewall when a new cluster node is connected. In particular, VMmanager increases the values of net.nf_conntrack_max and net.netfilter.nf_conntrack_max parameters controlling the maximum number of network connections to 1048576. This helps to avoid errors similar to nf_conntrack: table full, dropping packet causing the loss of network packets.

To change these parameters on the connected cluster nodes manually:

1. Connect to the server with VMmanager via SSH.

2. Enable ip_conntrack module:

   modprobe ip_conntrack

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3. Set the new value of the parameter net.netfilter.nf_conntrack_max. We recommend to increase that value to 1048576:

   echo "net.netfilter.nf_conntrack_max=1048576" >> /etc/sysctl.conf

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4. To apply the settings, execute the command:

   sysctl -p

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5. Check that the parameters have been changed:

   sysctl -a | grep conntrack_max

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   The response to the command should look as follows:

   net.netfilter.nf_conntrack_max = 1048576
   net.nf_conntrack_max = 1048576

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