;; Rather than 24 hours, minimum TTL is set to only 16 hours.; - This way, if a change is made as late as 5pm, we can guarantee that old; data will be flushed from anyones cache by the following morning at 9am.;; Exaple reverse .head file for 155.101.128$TTL 10800@ IN SOA ns.example.emulab.net. testbed-ops.example.emulab.net. ( 14 ; Serial (simple for now) 10800 ; Refresh 3 hours 3600 ; Retry 1 hour 3600000 ; Expire 1000 hours 57600 ) ; Minimum 16 hours IN NS ns.example.emulab.net. IN NS ns2.example.emulab.net.1 IN PTR private-router.emulab.net.