Should OpenVPN point to point tunnels be on different ports?

Question

The OpenVPN cookbook shows an example for site-to-site VPN (3 sites). They configured each tunnel on a unique port:

1. site A to site B: 1194
2. site A to site C: 1195
3. site B to site C: 1196

The author does not give any information about it. I didn't find anything useful in the man pages.
Is this a rule? Should we assign a unique port for every single point to point tunnel?

Answer 1

You would have to have them on unique ports. You can't have two applications listening simultaneously on a single port. So, in your example, because tunnels 1 and 2 both have an end on Site A, those endpoints must have unique ports. Hence the use of ports 1194, and 1195.

Now, because the VPN links 1 and 2 are using unique ports 1194 and 1195 on A->B, and A->C, the link between B->C can't use either of those ports, so the author chose 1196.

The port numbers used are arbirtrary, excluding assigned ports (1-1024), so the ports could be any 3 ports.

But, yes, the ports must be unique, at a minimum for each end-point at each site.