James Griffin agriffin at cpcug.org
Fri Jan 3 14:21:31 UTC 2003

LoChing wrote:
> Hi,
> This is the first time I post in this newsgroup and I don't have too
> detailed knowledge on DNS.
> Suppose my domain xxx.com was hosted in ISP NS servers (both primary and
> secondary), under normal case, all client query will contact
> the primary NS server?

Incorrect.  Client queries will be pseudo-randomly distributed among the
available servers.  

> Secondary only act the backup?

Incorrect.  The relationship between the "primary" (aka master) and
"secondary" (aka slave) is that they are "equals" when it comes to
providing answers.  The difference is that the primary/master gets the
information for the [sub]domains that it serves from data files (zone
database); where as secondary/slave servers get their information by
pulling the zone data (zone transfers) from the primary/master server.

> How long will primary NS consider as "DEAD" ?

What is "DEAD"?  The server is down?  Network access is down?  If the
primary/master server is down or unreachable and the secondary/slave is
up and reachable, then client queries that find their way to the
secondary will get authoratative answers from the secondary until the
"expire" time in the zone's SOA RR runs out.  This is how long a
secondary/slave nameserver will wait before considering its DNS data
stale if it can't reach the primary nameserver.


> LoChing

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