Network setup

This page explains how to set up a network for RuCTFE 2012. Here is step-by-step guide for Ubuntu 12.04.


  • Public NIC - eth0;
  • Private NIC - eth1;
  • Your team network is 10.23.N.0/24, where N is your team number.


  1. Install Ubuntu 12.04 Server.

  2. Configure your network in /etc/network/interfaces.
    For example:
    auto lo
    iface lo inet loopback
    auto eth0
    iface eth0 inet static
          address # your public ip
          netmask   # your netmask
          gateway # your gateway
    auto eth1
    iface eth1 inet static
          address 10.23.N.1
  3. Install OpenVPN.
    sudo apt-get install openvpn
  4. Unpack OpenVPN config (should be in your POC's mailbox).
    tar xzf teamN.tar.gz
  5. Copy your private key to teamN directory (which has been extracted from archive), rename it to teamN.key and run
  6. Now you should have your VPN up and running. Ping to check it.
    Note: once OpenVPN connection is established, it can take up to 1 minute before pings will actually fly. If you experience longer delays, feel free to contact us.
  7. Enable forwarding.
    Uncomment #net.ipv4.ip_forward=1 line in your /etc/sysctl.conf and then run sysctl -p
  8. Set up NAT for the networks outside VPN.
    iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
    Put this line to /etc/rc.local to run it automatically during boot.
  9. Set the IP of each team's workstation taking out one from 10.23.N.0/24 pool.
  10. Set the 10.23.N.1 as a gateway on each workstation.
  11. Set the virtual machines NICs bridged to the NIC of the machine hosting the VM.

If you have any problems with network configuration contact us via mailing list or send an email to

Network scheme

RuCTFE 2011 Network