1. Virtual Private Networking with OpenVPN Wim Kerkhoff Fraser Valley Linux Users Group April 15, 2004

2. FVLUG/OpenVPN presentation, April 2004 Wim Kerkhoff 2 The Basics: What is VPN? Short for Virtual Private Network Creates a private network over a public medium Typically uses for encrypting/securing traffic sent across the Internet between two locations Can also be used for single hosts on a LAN (even a wireless one) Nobody with access to the public network can see the traffic moving through the VPN – looks like garbage

3. FVLUG/OpenVPN presentation, April 2004 Wim Kerkhoff 3 What does OpenVPN offer? It’s Open Source (GPL), flexible, easy to setup Can tunnel any IP (layer 3) or Ethernet (layer 2) over a single UDP or TCP port Cross platform (Linux, *BSD/OSX, Windows 2000/XP, Solaris) Encryption provided via OpenSSL – tons of options/ciphers/etc Can use a 2048 bit shared key or digital certificates (PKI) Compression, traffic-shaping Works nicely with restrictive firewalls

4. FVLUG/OpenVPN presentation, April 2004 Wim Kerkhoff 4 How is OpenVPN different from other VPN packages? Only open source package that uses SSL Doesn’t need a special kernel module, unlike FreeS/WAN. Only the generic TAP/TUN driver is needed Very portable Easy – lots of configuration examples Traffic shaping per tunnel Can support hundreds of tunnels User-space: can co-exist with other networking packages eg IP/SEC. Can connect through an HTTP proxy Easier to set up on non-Win32 systems then PPTP

5. FVLUG/OpenVPN presentation, April 2004 Wim Kerkhoff 5 Modes Routed IP tunnels (layer 3)  More efficient then bridged ethernet tunnels  Easier to configure Bridged Ethernet tunnels (layer 2)  Can tunnel IP and non-IP traffic  IPX, NetBEUI, etc  Both sides of VPN see network broadcasts  Required for some LAN games

6. FVLUG/OpenVPN presentation, April 2004 Wim Kerkhoff 6 Routed IP Tunnels Possible Topologies:  Network Network  Network Host  Host Network  Host Host When doing VPNs with networks, an iptables script will have to created to set up IP Masquerading and some firewalling rules Uses “TUN” mode

7. FVLUG/OpenVPN presentation, April 2004 Wim Kerkhoff 7 Bridged Ethernet tunnel Really just operates like a transparent ethernet bridge. Hence, special IP tables, NAT magic, or routing is required Uses “TAP” mode Bridge tools (bcrtl) are required Need to create a script to bind eth1 and tap0 together into a bridged device called br0 Then assign an IP to br0

8. FVLUG/OpenVPN presentation, April 2004 Wim Kerkhoff 8 OpenVPN on Windows XP/2000 Double click installer Can be configured as a Windows Service that starts on boot Some simple configuration changes in the.ovpn config file Just need to put the shared key or certificates in

9. FVLUG/OpenVPN presentation, April 2004 Wim Kerkhoff 9 OpenVPN 2.0 Beta Series Can handle multiple UDP clients using a single UDP port Can support thousands of clients depending on hardware and network connection Has DHCP-like mechanism to push/pull specific settings to clients Better multithreading/SMP support Can run with least-privileges

10. FVLUG/OpenVPN presentation, April 2004 Wim Kerkhoff 10 Beyond OpenVPN 2.0 True point-to-multipoint Use a dynamic routing protocol to route through a larger and more complicated VPN cloud Reduce need to get route through a central server/office to access a system in another branch office

11. FVLUG/OpenVPN presentation, April 2004 Wim Kerkhoff 11 Conclusions… Definitely the way to go for anything VPN using Windows clients Way easier to setup then IPSec on either Windows or Linux Stable/Reliable OpenVPN website: http://openvpn.sf.net