>>If I drop our TTL value for our mail server to two hours how long does it
>>take to propagate thru the dns servers?
> It takes:
>>Currently the TTL value is set for 12 hours ...
> 12 hours.

plus Refresh interval if the slaves don't support NOTIFY.

Assume a 4 hour Refresh interval, the worst case scenario would be:

- slave makes a SOA query and finds it has the latest serial number
- you change your master
- 3.99+ hours later someone queries the slave and receives and caches
  the old IP with a 12 hour TTL
- 11.99+ hours later that IP is still in the cache

Worst case a total of just less than 16 hours.

-- 
[EMAIL PROTECTED]     "The avalanche has already started, it is too
Rod Dorman              late for the pebbles to vote." � Ambassador Kosh


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