I first noticed this issue after connecting as a client using WireGuard to Private Internet Access (PIA) from an MT2500A using the latest 4.1.1 firmware, but I’ve had the same problem after connecting to a remote Flint server.
The problem materialises as follows:
- The internet is working fine when connected via the MT2500A wth DNS set to “Automatic”. The MT2500A uses my local DNS server (on 192.168.1.1)
- I connect to a remote WireGuard server (PIA or the private Flint server) and again everything is working fine. A different public DNS server is used for these connections.
- I disconnect the VPN service and I’m no longer able to resolve DNS queries despite the DNS page of the MT2500A showing that it is on Automatic, connected to 192.168.1.1.
- I change the DNS to “Manual” and choose a public server (OpenDNS). Everything starts working again.
- I change back to “Automatic” and the server switches to 192.168.1.1. Everything continues working.
I haven’t had this happen universally on every occasion but it seems like the firmware isn’t always resetting DNS correctly when a WireGuard tunnel is closed down.