I recently setup IPv6 first-hop redundancy in my colocated environment using Mikrotik and VRRP. It didn’t work the same way I’d come to expect from using it in IPv4 environments and I set out to figure out why.
PowerDNS makes a mighty fine authoritative, and also recursive DNS server. They also recently added a DNS-aware DNS load balancer. This article deals with load balancing multiple backend caches to keep all of them hot and working the most efficiently.