52. Gracefully transitioning Internet domains through a IP address or ISP change change

Changing IP addresses and/or ISPs soon?

Making a smooth transition from one IP address to another isn't too hard though you need to do some proper planning and configuration ahead of time.

Here is a check list you need to do IN order:

Before you move: ----------------

1. Arrange with other sys admins to be both a backup DNS and SMTP server for you (they don't have to be the same machine or even service provider). I recommend to have at least (2) backup DNS servers and (1) SMTP server that are connected via entirely different ISPs. Setting up both backup DNS and SMTP servers is covered in their respective TrinityOS sections.

2. Next, you need to update your Internic registrar (Network Solution is one example). You need to tell the Internic your new backup DNS servers. Do this quickly as it takes time and some registrars constantly screw things up OVER and OVER and OVER.

3. Configuring backup SMTP is a matter of setting up an extra higher cost MX record(s) in DNS and adding your domain name to the /etc/mail/relay-domains file. Make sure you test this backup email mechanism as well. This will be added to trinityOS in the future.

4. Once you have #1 and #2 done, you need to change the DNS TTL (time to live) field in all of your domain zone files.. In each of your DNS zone records in /var/named, you need to change the TTL cache expiration # (last number in the SOA record). TrinityOS uses a TTL of "1D" or 24hrs. Change this "1D" to "60" (seconds) for ALL your domain name records and also change the serial # to reflect today's date. Restart named (/etc/rc.d/init.d/named restart) and wait 1 day until all the various DNS servers on the Internet time out your old cache settings.

   About to shut down your old IP address (24hrs after task #4): -------------------------------------------------------------

5. Go to your Internic registrar and update your account to reflect your new TCP/IP address for your main server. For Network Solutions, you should use their "host" form. Do NOT proceed until you get a notice back from your registrar that they have accepted your changes. Also note that though they might update your records, a "whois" might not reflect the changes as quickly as a "nslookup".

6. Once you have confirmed that the Internic has your new TCP/IP address, edit your various domain zone files in /var/named and change both the serial # to today's date AND change the TCP/IP address of your main NS record to reflect your new IP address.

7. Copy the old reverse DNS zone file for your old reverse IP zone file and now create a new reverse IP address zone file to reflect your new IP address.

8. Next, update the /etc/named.conf file to reflect the new reverse zone's filename from step 7.

9. Restart named (/etc/rc.d/init.d/named) to propogate your new zone files (w/ your new IP) to all the backup DNS servers).

   Changing your IP: -----------------

10. Update /etc/hosts, /etc/hosts.allow, /etc/sysconfig/network, /etc/sysconfig/network-scripts/ifcfg-eth* (* = your external NIC), and /etc/rc.d/rc.firewall with your new IP address.

    Shut down your box ------------------

11. Bring your box back up on the new network w/ the new IP

12. Have someone send you test email to make sure that DNS and email is working ok.

13. Finally, if everything is ok, re-edit all your domain zone files and update both the serial # and change the TTL back to 1D. Don't forget to restart named so both your DNS server and all your backups are updated.

14. Finally, make sure that all of your backup DNS servers accept new zone file xfrs from your new IP address. This security measure is controlled by their /etc/named.conf file.