I have a Fortigate 100D with 2x BT Business Infinity Fibre connections acting as WAN1 & WAN2.
The BT lines come with 5 static public IPs each and I have my DNS hosted through CloudFlare pointing at a static IP on one of WAN connections.
(Say you do a nslookup on mylesgray.com you will see 184.108.40.206 as the public IP).
We want redundancy for our A Records (for hosted websites, VPNs, ssh etc) but obviously the 2x BT lines have 2x different sets of public IPs, so if WAN1 goes down, we are dead in the water - no failover as the address is static.
I had looked up external DNS failover but that seems messy and very wrong to me (round robin annoys me). Then anycast came up as an option, however, Anycast seems to require and entire /24 block or in some ISP's casts even /22. We are running an enterprise level router so using BGP etc is not a problem.
Can anyone shed any light on how to achieve failover for DNS A-Records short of buying a /22 block of IPs or using Round Robin DNS?