Quote from: snarked on November 19, 2023, 08:52:56 AMALIAS is a non-standard RRtype which is not universally supported. If what you are attempting to do is load balancing, SRV and NAPTR records can do that. The only problem is that web clients typically don't fetch such records.
For what definition of ALIAS that exists, it is supposed to "take the place" of a CNAME at a zone's apex where CNAME is not permitted. Therefore, it should be a "Singleton" - so I don't see how multiple ALIAS records can exist for the same label, nor exist at other than a zone apex.
Another way to do load-balancing is to have multiple address records per label, and rely on DNS randomization as to the order the addresses are presented. However, there is no control over how often a particular record will be selected, thus it may tend to prefer the quickest responders over time.
alpha.fqdn.example.com 3600 IN AAAA 2001:db8::1
example.org 3600 IN ALIAS alpha.fqdn.example.com
; several records for servers' FQDNs:
alpha.fqdn.example.com 3600 IN A 192.0.2.1
bravo.fqdn.example.com 3600 IN A 192.0.2.2
; except charlie, charlie doesn't have IPv4, good for charlie!
;charl.fqdn.example.com 3600 IN A
alpha.fqdn.example.com 3600 IN AAAA 2001:db8::1
bravo.fqdn.example.com 3600 IN AAAA 2001:db8::2
charl.fqdn.example.com 3600 IN AAAA 2001:db8::3
; now the records for prod
www.example.com 3600 IN ALIAS alpha.fqdn.example.com
www.example.com 3600 IN ALIAS bravo.fqdn.example.com
www.example.com 3600 IN ALIAS charl.fqdn.example.com
www.example.com 3600 IN MX ; imagine an MX entry here
; for illustrative purposes below:
www4.example.com 3600 IN ALIAS alpha.fqdn.example.com
www4.example.com 3600 IN ALIAS bravo.fqdn.example.com
; this is the problem though:
www6.example.com 3600 IN ALIAS charl.fqdn.example.com