Multiple VPNs

Targets macOS
1

I have a server with multiple VPN’s. On startup or anytime it reconnected for any reason the Networkinterface IP’s change so do i have a way of associating IPs to a particular customer? How would you determine which network interface went with a customers VPN?

Thanks fo any help.

2

Can’t you assign an IP to a username/connection so they always connect and get the same IP address?