On 25/07/2019 22:17, Giles Coochey wrote:
Separate DNS servers must be on a different subnet according to RFC2182 (https://tools.ietf.org/html/rfc2182):
Secondary servers must be placed at both topologically and geographically dispersed locations on the Internet, to minimise the likelihood of a single failure disabling all of them.
I know that UPSs are physical, and subnets are logical, but the reasoning behind the requirement is due to having to be on a different infrastructure.
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Shock horror, replying to my own post, but in cloud cluster environments, you might consider anti-affinity rules to prevent multiple name servers going down at the same time due to a cluster node failure (i.e. rules to ensure that hypervisors keep different name servers on different hosts).
I know it doesn't help OP, who was looking for cluster based solutions, but the same applies if using load balancing virtual appliances, hosting IPs as name servers.