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

[Bug Hunter]

> 
> 
> the problem still happend even I can see the ip A record changed (which 
> means that Public DNS _really_ updated my A record)
> 
> How/what the problem will happen if the serial number don't change?
> How TTL works on DNS on real world?
> 

  The TTL (Time To Live) essentially tells the receipient DNS server how 
long to remember the address before assuming it has gone stale.

  If a TTL is 48 hours, the DNS server your machine contacted (the 
nameserver) will remember the answer from the domain's name server for 2 
days.

  For example, I have 1.1.1.1 as my dns server entry. I ask for 
www.microsoft.com.  Microsoft responds with 2.2.2.2, with a TTL of 48 
hours.

  For the next 2 days, 1.1.1.1 will remember the 2.2.2.2 answer and kick 
that back to you immediately.

  For some name server queries, the serial number is looked at to 
determine if a change has been made to the name server database.  If this 
has occurred, the local name server forgets what it had remembered and 
asks the domain name server for the new information. 

  For example, Microsoft changes their serial number by one.  One day 
later, you ask for www.microsoft.com. The 1.1.1.1 name server checks the 
remote serial number, sees it is different, forgets the 2.2.2.2, asks for the new 
address and gets 2.2.2.3.  It gives that answer to you.


bug