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I'm completely changing our WAN interface addressing (new ISP). Which DNS zone adjustments should I make to the various parameters (TTL, expire, etc.) to help propagate the changes out to the Internet in the quickest manner? I hacve a week until the changeover. Thanks for the input.

AaplMike
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Time to live TTL in seconds is the only thing that affects the time there could be different cached records on different locations. Therefore lowering it is efficient.

There is no correct value for the TTL: it depends on your needs. In situations where you have the same service on both IP:s, e.g. web server having same content, you can safely have longer TTL. Then, if you need to be sure that email won't arrive to the old server after the change, you could use extreme low TTL, like 300 for 5 minutes.

The only important thing is that you should do the change for the current TTL before changing the records. And, if you use a short TTL, remember to change it back afterwards.

Esa Jokinen
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    You also need to lower the refresh value in order for the slave nameservers of the zone to synchronize quicker (and/or making sure to use NOTIFY and/or controlling the slave nameservers and being able to force them to reload data) – Patrick Mevzek Jun 02 '17 at 19:28
  • Good point, Patrick! I've always used NOTIFY, so this was in my blind spot. – Esa Jokinen Jun 02 '17 at 19:31