I have the following home network setup:
- LAN: 172.16.0.0/24
- Proprietary router of my ISP (IPv4, Bridge-Mode -> Bridged to my FRITZ!Box router)
- Router & DHCP (FRITZ!Box) -> 172.16.0.1
- VPN, IPSEC (built-in functionality of the router, accessible via DDNS) -> 172.16.0.251 (VPN client IP)
- Synology DiskStation (Local DNS-Server) -> 172.16.0.10
The FRITZ!Box is configured to announce the DNS server's IP address to devices in the home network. This works fine when I connect my iPhone internally/via Wi-Fi; the client gets the correct DNS IP and the resolution of internal domains works as intended.
However, when I access the network via VPN, the name resolution fails. Interestingly Net Analyzer (iPhone App) lists 172.16.0.1 as my DNS server's IP address. It looks like the router doesn't tell my iOS device the DNS server's IP when connecting via VPN.
What am I missing here? Is that a general/known restriction or is this a functional restriction of my router or iOS?
Best Answer
When you connect to a VPN you don't get the regular DHCP from your LAN so your comparison with LAN devices, unfortunately, does not help in this case.
It's the VPN server that determines the DNS-server address the VPN client will receive, so you need to configure this on your FRITZ!Box. At least if it's possible, if not it seems the FRITZ!Box's VPN server will just send its own IP as the DNS-server address to the VPN client by default.