Don't muck with the DNS record. Use an "A record" associated with a secondary/floating IP; then simply move the IP associated with the A record to the new machi

Don't muck with the DNS record. Use an "A record" associated with a secondary/floating IP; then simply move the IP associated with the A record to the new machine and issue a gratuitous ARP. You can avoid setting arbitrarily low--but not low enough--TTL, etc.