Network setup for RuCTFE 2011

This page explains how to set up a network for RuCTFE 2011. Here is step-by-step guide for Ubuntu 10.04.


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


  1. Install Ubuntu 10.04 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 .
  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 directly to znick.