I agree, the descriptions on the properties sheet are a little confusing. So let's see if we can clear it up.
When a new record is dynamically added to a DNS zone, it is time stamped.
During the no-refresh interval, 7 days by default, the DNS server will not accept refresh attempts for this record. The time stamp will not be modified. Updates to the record are allowed, like if an IP address or name changed, but not refresh requests, This reduces the workload on the DNS server.
Once the no-refresh interval expires, the refresh period begins, 7 days by default. During this period, the DNS server will accept refresh requests for the record. If the DNS server receives a refresh request, the server will process the request, and update the timestamp for the record. Once the timestamp is updated, the clock for that record starts all over, with the no-refresh interval.
If the DNS server does not receive a refresh request for a record, and the refresh interval expires, then the server marks the record as stale. The next time the garbage collection process runs (this runs periodically in the background) any records that have been marked by the server as stale, will be removed.
So to summarize, the no-refresh interval is how long the DNS server ignores refresh requests for a record. The refresh interval is how long a DNS client has to refresh its record, before it gets marked as stale and eventually removed.
Key points to remember:
- Aging and scavenging must be configured at the server level (right click DNS server > set aging/scavenging for all zones) before zone settings will apply.
- Zones inherit aging scavenging settings from the server settings.
- You can set aging/scavenging settings on a per zone basis by clicking the aging button on the properties of the zone. These settings will override server settings. Zone specific settings will not apply if aging/scavenging is not enabled at the server level.
Hope this helps,