DNS scavenge with multiple DHCP lease times
We have the following configuration. Also attached is our DHCP configuration @ the top level. We have the default Server 2012 R2 options, "Dynamically update DNS records only if requested by the DHCP clients" with " discard A and PTR records when lease is deleted" ticked. We have credentials set for DNS dynamic update & our DHCP servers are added into the DNSUpdateProxy group. Scopes & counts as follows:
9 DHCP scopes with 1 day lease
12 DHCP scopes with 2 day lease
11 DHCP scopes with 8 hour lease
105 DHCP scopes with 8 day lease
Have done a lot of reading about the refresh + no refresh ideally being the same as the DHCP lease time, but assumption being DHCP lease times are same for all scopes. Our scenario is they are not, & so not really sure on the impact of different scavenging options
Majority are 8 day lease, so reading many blogs it mentions this should ideally match the total refresh. So values of 4 & 4 for no refresh & refresh, but then what is the impact of this on our scopes with 1day, 2day & 8 hour leases? Suppose the risk is they end up with duplicates until the zone is scavenged?
This is where I am thinking we should maybe configure DHCP to "always dynamically update DNS records" but they don't know if this actually required. My thinking is that if address is assigned to another computer DHCP can update DNS & we shouldnt have duplicates, then configure 4 + 4 days for scavenging. Or is this not required?
Did a current check on DNS & we have approx 1300 duplicate records as it stands, so not sure the A & PRT is being removed when the lease expires, which it should with default settings