Just to make sure I have TTL's understood.

[Scott Haneda]

Before I go out on a limb, I wanted to ask those who know more about  
this than I do.  I added a zone change to my primary server, in this  
case, setting the TTL's pretty low, as things were going to move  
around a bit in the beginning.  Waited a few weeks after adding it.

* The basic thing I am trying to understand, is *when* the slaves get  
the change, and what repercussions there are if it is slow.

Here is the zone:
ORIGIN .
$TTL 86400      ; 1 day
example.com              IN SOA  ns1.hostwizard.com.  
scott.hostwizard.com. (
                                 2008112501 ; serial *** I did change  
this ***
                                 14400      ; refresh (4 hours)
                                 7200       ; retry (2 hours)
                                 604800     ; expire (1 week)
                                 3600       ; minimum (1 hour)
                                 )
$TTL 3600       ; 1 hour
                         NS      ns1.hostwizard.com.
                         NS      ns1.nacio.com.
                         A       64.84.37.51

$TTL 300        ; 5 minutes
                         MX      10 gonepostal.hostwizard.com.

$TTL 3600       ; 1 hour
                         TXT     "v=spf1 ip4:64.84.37.0/26 ?all"

$ORIGIN example.com.
foo                     A       64.84.37.51
bar                     A       64.84.37.51


$TTL 300        ; 5 minutes
www                     A       64.84.37.51
pop                     A       64.84.37.6
smtp                    A       64.84.37.6

dig example.com MX
That will give me back the MX you see above. In this case, I am on a  
starbucks wifi, so they use whatever NS they are using.

At home, the same command, pointed to openDNS, gives back the new MX  
as well.

Now, if I run dig example.com MX @ns1.hostwizard.com I also get the  
new MX

Running dig example.com MX @ns1.nacio.com, which is my slave provide
example.com.		188	IN	MX	20 mx1.biz.mail.yahoo.com.
example.com.		188	IN	MX	30 mx5.biz.mail.yahoo.com.

It took openDNS, all of 6 or 7 minutes to get the change, I am now,  
hours later, not seeing the change in my secondary provider.  They  
also have ns0.nacio.com, ns1.nacio.com, ns2.nacio.com and  
ns3.nacio.com, all of which answer stale for this query.

Am I correct, in that, the 300 TTL I set, is correct, and what I  
should have done to prepare for a MX change to happen with as little  
problem/delay as possible?

What is the setting on a slave that determines when it should see my  
change?  My logs show the notifies going over, and being accepted.

I also provide a secondary, and to be honest, if I wanted to stall my  
secondary from accepting a primary notify, different than the TTL, I  
would not even know how to do that.

If the whois servers are listed with myself, and my secondary, and the  
secondary is now stale, for hours, what repercussions does this have?

I think, queries that are not cached by the local resolver of a  
internet user, go back to whoever is listed in the whois.  I am also  
pretty sure it does not pick one over the other, I see no way a client  
request could pick a primary over a secondary, I believe it happens at  
random, almost in a load balanced way, or perhaps it is distance  
routed, so the closest is first.

Either way, am I correct in that a secondary, is needed, if it is  
there, it must be in sync, as it is pretty evenly used by all clients  
requesting data from it, until their local resolver caches it?

Thanks, and as I said, I am just trying to understand this, so I have  
the correct date to provide a accurate support request.
--
Scott