Once the records are registered by clients in DNS server, if scavenging is not enabled, your dns server may have stale records which are not useful in your environment. Sometimes, this may also lead to a problem that dns server responding with different answers when a dns query is made.
This scavenging process will not be applicable for the resource records which are created manually. TTL value for these records will be zero. These records will not participate in scavenging process.
There are four important paremeters are available to make use of the scavenging.
- Scavenging interval
- Aging configuration
- No-refresh interval
- Refresh interval
Scavening interval:- This can be viewed by looking at the properties of a dns zone. Click on the scavenging tab and default time limit is 168 hours( 7 days). After enabling this, records which are not updated for 7 days will be automatically deleted.
Aging Configuration: This has to be set as 1 to enable scavenging process. Default value is 0.
No- Refresh Interval :- After a record is updated in the dns server, the record will not recieve any updates after this time period. Default value is 7 days. But if the IP address or hostname changes, that will be updated.
Refresh interval :- After the No-refresh interval set above, a record can wait for time period mentioned here to get an update. Default value is 7 days. For ex, a record is generated and no updates recieved for that record for the first 7 days. Within, the next 7 days, if the record doesn’t get any update, it will considered as STALE. This record in turn will be deleted after 7 days. So totally, ifyou leave the default configuration of 7 days in all the above parameters, stale dns records will be deleted after 21 days.
Hope it’s clear and useful.. 🙂