On Wed, Nov 09, 2005 at 11:18:07AM -0500, Tony Heal wrote: > I have a DNS server (Debian woody, bind v8.3.3-2.0woody2) that I need to > move. It has been suggested that I change the TTL to an hour so that all > name servers with anything cached will expire during the physical move of my > server. Thus reducing my downtime to the time it take to move the computer > hosting DNS. > > I am a little confused about what needs to be set. I would like the cache to > expire in 1 hour, so I think I need to change (see below) refresh to 1800, > expire to 3600. Is this correct? > > > @ IN SOA dns.mydomain.com. postmaster.mydomain.com. ( > 2005110200 ; serial number > 3600 ; refresh > 300 ; retry > 86400 ; expire > 900 ) ; minimum TTL > > I think that it means you need to change the TTL for each entry. In my BIND configuration, I have the line "$TTL 604800" at the beginning of each db file, which makes it apply to all entries in the file. However, if you want to set the TTL to 60 (for 1 hour) and then move the server, you need to wait for $time after you update the TTL, where $time is the length of the original TTL. In my case, I have my TTL set to 1 week. So, I would need to change it to 60, wait 1 week and then I could do it. The reason is that that resolvers that queried you 5 minutes before the change have the TTL set to whatever your previous TTL was. I hope that I correctly understood what you were asking. -Roberto -- Roberto C. Sanchez http://familiasanchez.net/~roberto
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