TTL question

[Kevin Darcy]

mahermick at gmail.com wrote:

>Hi Folks,
>
>I'm trying to understand the implications of not lowering the TTL for a
>record prior to it being changed.
>
>Taking a hypothetical situation - I have an Primary MX record with TTL
>of 3600 (1 hour) and no Secondarys (for arguements sake).
>
>If I changed the MX record would the maximum time my mail would be
>unavailable be one hour or is it possible that it could take longer?
>
Correct, but you are *required* to have at least 2 nameservers for a 
zone. So there's always going to some propagation time between them 
unless you make the change on all of them simultaneously (in BIND terms, 
that means they would all have to be configured as "type master").

                                                                         
   -Kevin