Hi,
I need to change my A record for my mail server to move it to another Public IP. What I wanted to do was change add a static NAT for the new entry as well as the old entry, then remove the old entry once I know that the change has propagated everywhere. However, my ASA won't let me have two static entries for the same internal IP.
How do I do this so when the record changes there is no delay on mail while the DNS change propagates?
Thanks.
Multiple MX records. Publish the new address in the MX first, wait for it to propagate, then change the A record.
If that won't work, then start up a second mail server on the same machine but listening to another port, and static the second IP's smtp to that. The source and destination combination will still each be unique, so the ASA won't give you any trouble about it.
K.J 44
Have you tried just adding a second IP on your Mail server interface. Then you could have 2 different static pointing to the same physical server. But it will depends if your Mail server application listen on both IPs.
If you plan the DNS change correctly you can get the DNS propagation down to a few minutes. Just enough time for a quick config change. Lower the TTL on the domain a few days before to something like 600 (ten minutes) so that any DNS record won't be cached for longer than that. Once the change has propagated then you can reset the TTL to a normal value.
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