OpenVPN different tun interfaces with same virtual gateway

Theodor

Hello all,

I was playing around with OpenVPN to understand better how it works and I am struggling to understand what problems might give my configuration.

I have two clients connecting to the same server, I want them to redirect the traffic and get the ip adress of my VPN, I am using different ip addresses but same virtual gateway:

#A.conf
[...]
ifconfig 10.10.10.2 10.10.10.1

#B.conf
[...]
ifconfig 10.10.10.3 10.10.10.1
The ifconfig command gives the following:

tun0
10.10.10.1 via 10.10.10.2

tun1
10.10.10.1 via 10.10.10.3
in this way I can use one single iptable rule since both the clients are on the same gateway and all is working without problems, both my clients get the ip adress of my VPN and I can surf internet without issues.

I know I can change the gateway and add more iptables rules, just I am curious about what problems could give my configuration and why people say not to use it even if it is working great for me.

Thank you!

Theodor

Hello all,

I was playing around with OpenVPN to understand better how it works and I am struggling to understand what problems might give my configuration.

I have two clients connecting to the same server, I want them to redirect the traffic and get the ip adress of my VPN, I am using different ip addresses but same virtual gateway:

#A.conf
[...]
ifconfig 10.10.10.2 10.10.10.1

#B.conf
[...]
ifconfig 10.10.10.3 10.10.10.1
The ifconfig command gives the following:

tun0
10.10.10.1 destination10.10.10.2

tun1
10.10.10.1 destination 10.10.10.3
in this way I can use one single iptable rule since both the clients are on the same gateway and all is working without problems, both my clients get the ip adress of my VPN and I can surf internet without issues.

I know I can change the gateway and add more iptables rules, just I am curious about what problems could give my configuration and why people say not to use it even if it is working great for me.

Thank you!
[/quote]

TinCanTech

Theodor wrote why people say not to use it

who says wot now ?

Theodor

Maybe the first post was confused, what I meant is the following:

is it possible to have two clients connecting to one OpenVPN server assigning different IP addresses but same gateway ip? With the following configuration:

client A:

remote <ip openvpn server>
ifconfig 10.0.8.0 10.0.8.1
redirect-gateway autolocal
dhcp-option DNS 8.8.8.8
secret secret.key

Client B:

remote <ip openvpn server>
port 3221
ifconfig 10.0.8.0 10.0.8.2
redirect-gateway autolocal
dhcp-option DNS 8.8.8.8
secret secret2.key

Executing ifconfig on the server I get the following result:

tun0
inet addr 10.0.8.0 destination 10.0.8.1

tun1
inet addr 10.0.8.0 destination 10.0.8.2

If I connect the two clients at same time it works fine I can surf internet and I get the ip adress of my VPN server after using the command iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE.

Even if it is working I was wondering if that is a correct configuration or might give some problem since the gateway ip adress are the same both for tun0 and tun1 interface.

Thank you

TinCanTech

It sounds like you have it working ok. Using iptables to masquerade your client IP address is the usual method.

I don't know why you have two tun interfaces .. I don't think you know either.

Theodor

TinCanTech wrote It sounds like you have it working ok. Using iptables to masquerade your client IP address is the usual method.

I don't know why you have two tun interfaces .. I don't think you know either.

Thank you for your answer, I have two tun interfaces because I have two computers connecting to my VPN.

When I connect with my first computer on the remote VPN server a tun0 interface is created and when I connect with my second computer the tun1 is created.

The interface tun0 and tun1 are on the server, on the clients I have only 1 interface as it should be, I was just wondering if using the same gateway ip adress on my clients would create problems or its ok.

ifconfig command on server:

tun0
10.0.8.0 destination 10.0.8.1 [client A connect ed]
tub1
10.0.8.0 destinaton 10.0.8.2 [client B connected]