How to test if a vpn has been established correctly between two pc's?

Question

I'm trying to connect two pc's using IPsec and StrongSwan.
The first pc, which I want it to be the server runs openSUSE and the client pc runs Fedora. So after installing StrongSwan in the first pc what kind of test can i do to see if there is a tunnel between the client and the server? For example could I send a file from the client to the server, apart from just ping one another.

Answer 1

If you have full access to the server box, the best thing you can do is to check that traffic from the client arrives from the correct interface. Something like:

tcpdump -i <ipsec-interface> -n

You should see traffic from the client here.

UPDATE: Similarly, traffic from the server should arrive on the client through its IPSec interface and can be inspected with tcpdump there.

Answer 2

ping should be enough for tunnel mode. try to look for this:

tcpdump -i <ipsec-interface> -n 'esp or udp port 500 or udp port 4500'