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Secondary DNS replication

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by johnscrooby

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Hi..

Im hosting a primary DNS server for 200 domains at my office. The secondary is off site. In the properties page of the SOA for a domain in the DNS mmc there are 3 fields, namely, Refresh interval - retry interval and expires after. Can anyone shed some light on exacly what these fields refere to? You can also set the TTL for hte SOA, but what do the numbers refere to. Is it day, hour minuite seconds, or what? All these fields direcly influence DNS replication and the amount of time your secondary will stay up in the event of a primary failiure - so - can anyone help?

3 replies

by bowieb

All of the fields are in seconds.

'Serial' is the serial number of the zone. The secondary server compares this with it's current information to determine if it needs to update it's information.

'Refresh Interval' is how often the secondary server refreshes it's information about this domain.

'Retry Interval' is how often the secondary server retries after the original refresh fails.

'Expires After' is now old the information can be before the secondary server will stop using it.
'TTL' is 'Time To Live'. This controls how long other DNS servers on the Internet will cache information about records in this zone before querying your name server again. TTL can also be specified for individual records in the zone.

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