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
  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
  4. To apply the settings, execute the command:

    sysctl -p
  5. Check that the parameters have been changed:

    sysctl -a | grep conntrack_max

    The response to the command should look as follows:

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