A domain might have a "A" tag pointing to an address, so we can go from name to address:
jupiter.sun.csd.unb.ca. A 131.202.3.8

We can do a reverse lookup on an IP address, because IP addresses are also located in the DNS tree:
8.3.202.131.in-addr.arpa. PTR jupiter.sun.csd.unb.ca

Aliases have a "CNAME" tag pointing to a domain:
unix.unb.ca. CNAME jupiter.sun.csd.unb.ca

However, there's no equivalent to PTR for aliases -- there's nothing under jupiter.sun.csd.unb.ca that points back to unix.unb.ca -- so doing a reverse CNAME lookup is impossible.

You need to either get the zone file from the DNS server (which you said you couldn't) or from the file system.

In reply to Re: DNS aliases by ikegami
in thread DNS aliases by UberGeek

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