Dns slave server not updating
If there is a backup copy, the slave server reads it on startup and later checks with the master server to see if the master server has a newer copy instead of loading a new copy of the zone immediately.
A second name server splits the load with the first server or handles the whole load if the first server is down.
We chose to start our serial number at 1, a logical place to start.
But many people find it more useful to use the date in the serial number instead, like 1997102301.
The polling interval is one of those numbers in the SOA record that we haven't explained yet.
(BIND Versions 8 and 9 support a mechanism to speed up the distribution of zone data, which we'll describe later.) A slave name server doesn't need to retrieve all its zone data over the network; the overhead files, directory /var/named primary db.primary 249.249.192.db.192.249.249 primary 253.253.192.db.192.253.253 primary 0.0.127.db.127.0.0 cache .
This is critical: whatever format you choose, it's important that the serial number always increase when you update your zone data.