You don't to choose a TTL once and for all, though.
In other words, in BIND, "minimum" is not really minimum.
By reducing the TTL, we force the outside servers to update their data more frequently, which means that any changes we make when we actually move the system are propagated to the outside world quickly. Unfortunately, we can't safely use a TTL of zero, which should mean "don't cache this record at all." Some older BIND 4 name servers can't return records with a TTL of zero, instead returning null answers or SERVFAIL errors. The easiest change is to lower the TTL in the $TTL control statement in the to each resource record.
If you lower the default TTL, though, the new, lower default applies to all zone data, not just the address of the host being moved.
A name server caching the old address record just before the change could have the wrong address for as long as three hours.
A loss of connectivity for three hours is unacceptable, though.Suppose we know that one of our hosts is about to be moved to another network.