[NTLUG:Discuss] why does the web site cannot be 'see' fromoutside (internet)?

[Greg Edwards]

m m wrote:

> according to Madhat said (see below), if the serial number not changed, 
> it will not send out to the word even you re-read/re-start/reload the 
> named? right?
> 

Short answer:

The DNS master has all source info for your domain (yourdomain.com).  A 
    DNS secondary is updated by the master.  Other DNS servers keep a 
copy of the IP for the named computer (ie yourbox.yourdomain.com).

When a client needs to lookup an IP its nameserver broadcasts a request 
which eventually gets answered by a secondary or master for that domain. 
  That IP is kept in the clients nameserver until the TTL expires.  The 
nameserver will ask a secondary or master for the IP next time a client 
requests it.

A master will read the host info either when it's started or a notice to 
reload is given to it.  If the serial # has been changed the master will 
inform the secondaries (slaves) who will then do a zone transfer.

There is actually allot more going on than this but this should give you 
an overall simplified picture.

-- 
Greg Edwards
New Age Software, Inc.
http://www.nas-inet.com