Symptom:

Your servers are moving to new addresses, but you realize that it’s not as simple as just changing the IP settings of the boxes. There are issues to consider.

Problem:

If you move all of your servers to new addresses, all at once, nobody will know where to find them. But if you change the address records in advance, nobody will be able to find them in the interim.

Also, your domain registrar (or the administrator of your parent zone) may have your servers’ addresses on file, and these records are (typically) used to create the glue records for your servers, in the parent zone. These glue records are often given fairly long TTL’s, such as two days, and you have no way to reduce the TTL’s in advance of the move.

Solution

The best way to move the servers to their new addresses is to assign both new and old addresses to the servers at the same time. Then update all necessary DNS records, both in your zones and at your domain registrar, and wait. Once the old glue records have expired (typically a little over two days after requesting the change at the registrar), you can remove the old addresses from the servers.

If this is not feasible, then move them to their new addresses one at a time. This takes advantage of the fault tolerant nature of the DNS protocol. Be very sure not to reboot one server while the other is in transition.

For example, assuming there are just two servers, the sequence of events might be thus:

• Edit the A record of the master server, changing it to the master’s new address.
• Use your domain registrar’s website to update the registered server address for your master server.
• Move the master server to its new address. Be sure to restart at least the DNS service itself.
• Update the slave server’s master server address, for all zones.
• Wait until the old glue record has expired, typically about two days after the change was made using the registrar’s website.
• Repeat steps 1-3 for the slave server.
• If there are zone transfer restrictions on the master, make sure the slave is allowed to get zone transfers to its new address.