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When Correcting A DNS "CNAME", Maybe Delete Before Adding

Very few registrars allow multiple "CNAME" addresses, for a single DNS host.

When I diagnose DNS address problems, I generally recommend
Add the addresses highlighted in green.
Remove the addresses highlighted in red.
I find that it helps to have the old address visible, while the new address is being composed. This does not always produce the desired result, unfortunately.

Many registrars do not allow multiple "CNAME" addresses, for DNS hosts - and the zone editors reject new address attempts.

When DNS addresses for a Blogger custom domain need to be corrected, I recommend
Add the addresses highlighted in green.
Remove the addresses highlighted in red.
I recommend correction in this order, so the blog owner can view the current (incorrect) addresses, while adding new (correct) addresses. This compensates for various zone editor syntax oddities.

Making corrections in this order - adding correct addresses, then removing incorrect addresses - does not always produce the anticipated results. If the zone editor checks as each individual address change is made, we see the result.


"That name is reserved (already in use)."



Some zone editors check, immediately, when a second "CNAME" is entered, for a given "Host" address. When multiple "CNAME"s are forbidden, and the zone editor checks for multiple "CNAME"s immediately, we have a problem.

Other zone editors check for a correct address complement, when Saving multiple zone editor changes - after all additions and removals are successfully made and verified. These zone editors do not present a challenge - as long as the blog owner removes all incorrect addresses.

When the incorrect addresses are not removed properly, we see the result.

That name is reserved (already in use).

This leads the blog owner to cancel the recommended correction - and we wait, in vain, for the domain to come online.

In a worse case scenario, we can even end up with another case of "Another blog ...".

Right now, though, we can only diagnose the problem, one domain at a time.



Some registrars have zone editors which forbid multiple "CNAME"s for specific addresses - and check, one entry at a time, for mistakes. This may cause a problem, with a #Blogger blog owner making custom domain DNS address corrections, when instructed to "Add addresses highlighted in green.", then "Delete addresses highlighted in red."

Comments

Aaron Johnson said…
That's extremely helpful! And your post is extremely detailed. I'm always careful when using cname records.

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