Vpn clients not updating dns
Both are valid, but have differences in configuration. For more information on route-based and policy-based, see IPsec VPN overview.
Route-based VPN configuration requires two security policies to be configured (one for each direction of traffic) to permit traffic over the VPN virtual interface, and you must also add a static route entry for that VPN interface or the VPN traffic will not reach its destination.
All configuration and communication with that tunnel depends on the IP addresses as reference points.These entries are kept up to date by your computer sending its current IP address to the DDNS server to ensure its entry is always up to date.When other computers want to contact your domain, their DNS gets your IP address from your DDNS server.A domain name assigned to this computer is resolved by any DNS server having an entry for the domain name and its static IP address.
The IP address never changes or changes only rarely so the DNS server can reliably say it has the correct address for that domain all the time.
To use DDNS servers, you must subscribe to them and usually pay for their services.