I have just finished setting up a basic VPN using OpenVPN. I’m able connect on all the clients (2 clients currently), and everyone can see each other (server + clients). I can access services on each machine over the VPN, share files, ping, etc. I would like to tunnell all of the client’s traffic through the VPN, not just filesharing and things like that.
I’m running OpenSUSE 11.1 for the server, and my two clients are Windows XP machines.
Searching around I found a bit about changing the routing on the client, but this is something I do not know anything about. I was able to install Wireshark on the clients and the server and do a bit of testing.
On client1, I decided to play with the routing table a bit. Here is the line I changed in its original form:
Network Destination Netmask Gateway Interface Metric
0.0.0.0 0.0.0.0 192.168.10.1 192.168.10.111 10
I deleted that line and added this line:
PS C:\Documents and Settings\Administrator> route add 0.0.0.0 mask 0.0.0.0 10.1.0.1 IF 3
Network Destination Netmask Gateway Interface Metric
0.0.0.0 0.0.0.0 10.1.0.1 10.1.0.2 1
This breaks the connection to the outside world on the client though. The VPN connection is still fine, and I can ping the other LAN machines not on the VPN, I just cannot get outside. So this leads me to believe I’m doing something wrong here 
Also, just for fun, I tried adding a route to a specific website and then pinging it from the client. Here’s what I did, and the result:
PS C:\Documents and Settings\Administrator> route add 207.97.211.30 mask 255.255.255.255 10.1.0.1 IF 3
PS C:\Documents and Settings\Administrator> ping clusty.com
Pinging clusty.com [207.97.211.30] with 32 bytes of data:
Request timed out.
Request timed out.
Request timed out.
Request timed out.
While I was pinging on the client, I had wireshark listening to the TAP interface on the server. The ping packets would show up on the server, but they would stop there.
I have the feeling that I need to do something on the server so that it knows what to do with these outgoing packets it receives on the VPN, but I do not know how to set this up. Here are the details on the setup:
Server: OpenSUSE 11.1
LAN IP: 192.168.10.108
VPN IP: 10.1.0.1
openvpn version: 2.0.9 x86_64
server.conf:
port 1194 # or any other port you want to use
dev tap
tls-server
cd /etc/openvpn/easy-rsa/2.0/keys
ca ca.crt
cert server.crt
key server.key
dh dh1024.pem
tls-auth ta.key 0
mode server
duplicate-cn
ifconfig 10.1.0.1 255.255.255.0 # openvpn gateway
ifconfig-pool 10.1.0.2 10.1.0.11 255.255.255.0 # ip range for openvpn client
push "dhcp-option DNS 10.1.0.1" # push DNS entries to openvpn client
push "dhcp-option DNS 10.1.0.2"
push "route-gateway 10.1.0.1" # push default gateway
mtu-test
tun-mtu 1500
tun-mtu-extra 32
mssfix 1450
ping 10
ping-restart 120
push "ping 10"
push "ping-restart 60"
push "route 10.1.0.0 255.255.255.0 10.1.0.1"
comp-lzo
status openvpn-status.log
verb 4
Client 1: Windows XP
LAN IP: 192.168.10.111
VPN IP: 10.1.0.2
openvpn version: OpenVPN 2.1_rc18
client.conf:
port 1194
dev tap
remote 192.168.10.108
tls-client
ca ca.crt
cert client.crt
key client.key
tls-auth ta.key 1
mtu-test
tun-mtu 1500
tun-mtu-extra 32
mssfix 1450
pull
comp-lzo
verb 4
Client 2: Windows XP
LAN IP: 192.168.10.110
VPN IP: 10.1.0.3
openvpn version: OpenVPN 2.1_rc18
client.conf:
(same as Client 1)
So as it stands right now, all 3 machines can see each other and talk to each other just fine over the VPN. I want the clients to be able to push all of their network traffic through the VPN though - eventually I want to be able to use an open WiFi hotspot and connect to the VPN at my home, and tunnel all of my internet traffic through my home (I’m currently using SSH tunnels, and I wanted to give VPN a try).
Any ideas/suggestions? Need more info? Thank you for taking the time to read all of this, every help/comment/suggestion is appreciated!