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We currently have a number of client computers linked up to a database server (MS SQL 2008) for replication. The database server recognises the computers based on their Windows hostname. We are using dynamic IP addresses at this time because we tend to change the computers’ hardware quite frequently, and so the MAC address may be different. Unless static IP has a good way for us to manage frequent changing of MAC addresses, we are keeping it to dynamic IP.

The problem with dynamic IP addresses, however, is that when a client fetches an new IP from the DHCP, ie, there is a change in the IP address, there is going to have a downtime for the hostname to reflect the new IP address, the client’s DNS cache of the hostname to reload, and also the server’s DNS cache to reload to see the new IP from the hostname. All of these have different timings and the delay can be really bad at times. Restarting the computer doesn't work all the time too.

The clients are on Windows 7.

How can I eliminate the amount of downtime required when there is a change in IP in the case of dynamic IP addresses?

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As you noted, DNS replication takes time as it propagates across devices. You would have to manually flush the DNS cache on the SQL server (and any other devices in the chain) every time you a change is made. Have you looked into disabling DNS caching and forcing all devices to query the DNS server(s) exclusively?

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Flushing all devices in the chain manually is not a good idea for me. :( I haven't looked into disabling DNS caching and force devices to query DNS servers exclusively. Would this completely eliminate the time required by DNS replication? – xenon Jun 6 '14 at 5:51

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