[sf-lug] SF-LUG DNS
jim at well.com
Tue Nov 17 21:06:22 PST 2009
jim was studying diligently until the dentist
pulled out one of his teeth and filled him with
pain pills. jim will study more in the morning.
On Tue, 2009-11-17 at 12:17 -0800, Rick Moen wrote:
> Quoting Michael Paoli (Michael.Paoli at cal.berkeley.edu):
> > Yes, definitely still stuff to be done (I keep hoping Jim or someone
> > else will get SF-LUG.COM. DNS squared away before the secondary expires
> > the zone ... but if the timing gets too close on that, I plan to correct
> > it - and in the meantime Jim Stockford and/or other SF-LUG.COM.
> > systems/DNS administrators can contact me if they need assistance or
> > have questions).
> If need be, it's simple to prevent zone expiration by temporarily
> telling the secondary that it's master for the zone (until the
> replacement master is ready).
> > Actually, by coincidence, turns out the "new" (substituted) master DNS
> > server is ... well, will be anyway, on the same IP (host is there, but
> > last I checked it's not yet serving up DNS nor particularly being DNS
> > for SF-LUG.COM.).
> OK, good for me, then. ;-> Everything should Just Work when Jim has
> the master DNS back online.
> > # cat var/named/chroot/var/named/sf-lug.com
> > $TTL 86400
> > $ORIGIN sf-lug.COM.
> > @ IN SOA ns1.sf-lug.com. jim.well.com. (
> > 2007102904 ;Serial
> > 3600 ;refresh period
> > 3600 ;retry period
> > 1209600 ;expire period
> > 10800) ;minimum TTL period
> > ;
> Minor correction: The last SOA sub-field hasn't signified "minimum TTL
> period" since BIND4 days. The above annotation is a dusty holdover,
> probably copied from an old example file, and should be replaced. The
> new-er purpose of that subfield is "negative TTL" aka "negative
> caching", which is how many seconds a nameserver should cache a NAME
> ERROR (NXDOMAIN) record.
> FYI, the value you specify, 10800 = 3 hours, is the longest time period
> for negative caching allowed by RFCs.
> FWIW, I tend to use these values in SOAs:
> 7200 ; refresh 2 hours
> 3600 ; retry 1 hour
> 2419200 ; expire 28 days
> 10800 ; negative TTL 3 hours
> [snip suggested steps when moving master DNS]
> > Yes, ... not quite the situation in this case.
> True, those remarks having been based on the assumption of moving master
> DNS to a new IP.
> It's still good to let your secondaries know about planned downtime.
> Which of course means it's a good idea to keep contact information in
> your /etc/named.conf[.local].
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