Updating hosts file multiple servers
There are now a number of alternate Open Source DNS servers some of which stress performance.These servers typically do NOT provide caching services (they are said to be 'Authoritative only' servers).There can be any number of slave DNS's for any given zone.Slave status is defined in BIND by including 'type slave' in the zone declaration section of the file as shown by the following fragment.Both servers could be any combination of master-slave, slave-slave or even master-master.
When a master DNS receives Queries for a zone for which it is authoritative then it will respond as 'Authoritative' (AA bit is set in a query response).Example configuration files for a slave DNS are provided. The definition of a slave server is simply that it gets its zone data via zone transfer, whereas a master gets its zone data from a local file system.The source of the zone transfer could just as easily be another slave as a master. A DNS Caching Server (frrequently called a Resolver) obtains information from another server (a Zone Master) in response to a host query and then saves (caches) the data locally.If a DNS server receives a query for a zone for which it is neither a Master nor a Slave then it will act as configured (in BIND this behaviour is defined in the file): A master DNS server can NOTIFY zone changes to defined (typically slave) servers - this is the default behaviour.NOTIFY messages ensure zone changes are rapidly propagated to the slaves (interrupt driven) rather than rely on the slave server periodically polling for changes.