We have a main dns .123 server and a backup dns .789 server. All of our remote sites have 2 spots in the Cicso ASA router for DNS. We had the main dns .123 and the secondary DNS .789 in those spots . It was changed so that primary dns.123 was our main dns server and then 188.8.131.52 for the secondary in case our connection went down between us the remote sites could still work. They were divided up so some of the sites used our main DNS.123 server and 184.108.40.206 as the secondary dns and some sites used our backup DNS.789 and then 220.127.116.11 for secondary.
Do you see any problem with this? I know there are some debates as to whether to use google dns or the ISP DNS, but other than that?