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Only route DNS on IPv6 cellular network

Posted: Mon Nov 19, 2018 7:39 pm
by ivant
I would like to only route DNS request through the vpn tunnel on iOS. I can successfully do this when connected on wifi (IPv4) I have a custom openVPN client using https://github.com/OpenVPN/openvpn3. On iOS created a custom network extension Packet Tunnel where I set up the DNS servers, and only include the DNS routes in the tunnel, I exclude IPv4 default route in the tunnel (so a split tunnel).

However once the iOS device is only on cellular data which is IPv6, the DNS doesn't appear to go to the VPN. If I have the client (cellular data) connected with full tunnel, it looks like the DNS is handled via IPv4, but in split tunnel it appears DNS happens with the IPv6 DNS server that the carrier sets up.

Anyone with insight into this would be very helpful. Thanks.