Network setup for RuCTFE 2009

This page explains how to set up a network for RuCTFE 2009. Here is step-by-step guide for Ubuntu 8.04.


  • Public NIC - eth0;
  • Private NIC - eth1;
  • Your team network is 10.N.0.0/16, where N is your team number (see registered teams).


  1. Install Ubuntu 8.04 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.N.0.1
  3. Install OpenVPN.

    sudo apt-get install openvpn
  4. Decrypt and unpack OpenVPN config (should be in your POC's mailbox).
    gpg teamN.tar.gpg && tar xf teamN.tar
  5. Copy OpenVPN keys and config to /etc/openvpn.
    sudo cp teamN/* /etc/openvpn
  6. Restart OpenVPN.
    invoke-rc.d openvpn restart
  7. Now you should have your VPN up and running. Ping to check it .
  8. Enable forwarding.
    Uncomment #net.ipv4.ip_forward=1 line in your /etc/sysctl.conf and then run sysctl -p
  9. 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.

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