We had a new BT Business Broadband ADSL line installed at work today with a static IP address, and are using a Draytek Vigor 2860 router.
Before the ADSL line is established (after a router reboot, say), in
Online Status -> Physical Connection -> LAN Status -> Router Primary DNS and Router Secondary DNS
shows correctly the DNS router addresses I had assigned, namely the Google DNS servers 18.104.22.168 and 22.214.171.124
As soon as the ADSL line connection is established, some 10-20 second later, these addresses are changed to what I presume are BT DNS servers (the IP addresses vary after each reboot).
Has anyone met this? And do you know how to prevent BT's 'forced' DNS routers overriding the ones we specify, for the Draytek 2860 specifically?