Network scheme

PHDays CTF 2017 Network

    We expect a lot of teams.

    Team network for team N is: 10.A.B.0/24, where A = 60 + N / 256, B = N % 256.

    If it seems difficult, just enter a team number
    to see instructions for your team.

Set up virtual machines

  1. Install VirtualBox.

  2. Download router and test images (mirrors: router and test image)

  3. Import both images to VirtualBox: "File → Import Appliance..."

  4. Check router image settings. Go to: "Settings → Network → Adapter2". Make sure that it is bridged to your real, hardware network adapter. It is preferable to use Ethernet adapters for bridging rather than Wi-Fi adapters.

  5. Check test image settings. Make sure that Adapter1 is bridged to your real network adapter.

  6. Start both virtual machines. You will see some instructions on a logon screen.

  7. Follow instructions on the logon screen and enter your team number to configure the network:
    router image:
    eth0 — this is your uplink. Address is obtained via dhcp by default. This interface is attached to NAT in VirtualBox, so make sure that you have an internet connection on your physical host;
    eth1 — this is your internal interface. It should be automatically set to: 10.A.B.1.
    test image:
    eth0 — it should be automatically set to: 10.A.B.3 and gateway: 10.A.B.1.

  8. You should use following network settings for your team's PCs during the game (or virtual machines setup):

    IP      = 10.A.B.128 - 10.A.B.255
    Netmask =
    Gateway = 10.A.B.1
    DNS =

Set up VPN connection

  1. Follow the instructions sent on your email (if not, please send message to: to obtain your OpenVPN config.

  2. Copy the config to /etc/openvpn/*.conf (for example to /etc/openvpn/phdays.conf).

  3. Restart OpenVPN on your router (/etc/init.d/openvpn restart).

  4. Check network connectivity. You should be able to ping 10.C.B.1 from your router and testimage(C = 80 + N / 256, N is your team number).

  5. Check your availability at (not available after competition)

  6. Leave both images running. You can shut down your testimage when the game starts.