SOLVED: Should Scavenging Be Configured On All DNS Servers and Zones?

The short answer is yes, Scavenging that should be configured on each of your DNS servers. That is also what Microsoft recommends.

What is DNS Scavenging?

DNS scavenging simply automatically deletes old DNS records. If you don’t enable DNS scavenging, you can have your DNS records with the same IP pointing to different devices. For example, if your PC is DHCP’d IP address 10.1.1.10 it will have a DNS record like MyPC1 = 10.1.1.10. What happens a few years later when that machine is replaced? Nearly all DHCP servers will reuse addresses that are not renewed within 7 days so after a week of your old machine being off the network, DHCP will give that address to a different computer AND it will create a new DNS entry. Now you will have MyNewPC1 = 10.1.1.10 but without scavenging the old MyPC1 will also point to 10.1.1.10 in your DNS. That makes name resolution very confusing.

Should Scavenging Be Enabled on ALL DNS Servers?

However, configuring DNS Scavenging is not technically required to be configured on each server and here is why. Windows DNS changes (i.e. deletions made by scavenging on one of the DNS servers) are replicated to all of the DNS servers. But think about what happens when one of your DNS servers goes away (i.e. gets old and decommissioned). If that was the only server with the DNS scavenging configured, there will be no more scavenging. As such it is best practice to configure identical DNS scavenging settings to all of your DNS servers.

Do DNS Configuration Settings Automatically Replicate To Other DNS Servers On The Same Domain?

We have often wondered why DNS settings like DNS scavenging are not replicated automatically to each server. We have never run into a situation were we wanted one DNS server to have a different configuration from another DNS server on the same Windows domain. That being said, we are certain there is a scenario in which automatic replication of DNS settings would be a bad thing, so Microsoft Windows Domain Controllers do not replicate their DNS configuration… it is a manual process.

Should DNS Scavenging Be Configured on All DNS Zones Including Reverse/PTR Zones?

As far as setting up scavenging on all zones, we say yes. Again, we are sure there are odd situations in which DNS scavenging should not be configured, but thus far we have never come across one. We always enable scavenging on all DNS zones.