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Altostratus
AltostratusCannot create a CNAME for a domain root
My customer has a site to be hosted behind GTMs. The ISP is authoritative for site.example.com. The GTMs are authoritative for wip.example.com. They want the site to be accessible via site.example.com...
Indeed a common issue. The RFC you quote on MX records is referring to the right hand side, the rrdata part of the MX record - mail.site.example.com in your case cannot be an alias.
As I recall this explained in the O'Reilly book by Liu, "a name can be a cannonical name or an alias, but not both".
A few solutions:
- a GTM in authoritative screening mode in front of site.example.com servers eliminates the need for aliasing altogether. If the name isn't a WIP, it falls through to the pool member(s) and gets answered by the authoritative NS. Tough to do in this case.
- have the parent rr DNS across all the possible answers, then have the LTM/web server redirect to a WIP name handled by GTM.
- have the ISP delegate site.example.com to GTM. In this case, it would be a zone and a WIP. That's ok. ;-)