Reducing DNS bandwidth
*Refresh - 86000 - This is time(in seconds) when the slave DNS server will refresh from the master. This value represents how often a secondary will poll the primary server to see if the serial number for the zone has increased (so it knows to request a new copy of the data for the zone). It can be written as “23h88M” indicating 23 hours and 88 minutes. If you have a regular Internet server, you can keep it between 6 to 24 hours.
There is constant bandwidth usage between primary and secondary(backup DNS) servers. This depends a lot on the Refresh value. If the refresh value is say 3 hours, your secondary server is polling your primary server every 3 hours and updating the cache. Lets assume you have a 1000 zone files, each with 3 hours refresh rate. You can imagine the bandwidth that must be getting used. This is especially true if the servers are on 2 separate physical servers.
An increase in the Refresh rate can effectively reduce bandwidth usage between the primary and secondary server.
BEWARE! Any name or label that appears on either the left or right-hand-side of a resource record that does not have a terminating full stop will have the origin added to the name/label. Missing full stops are one of the most common causes of error in DNS zone files.
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