DNS entries to Alias two completely different domains.

[David Hill_6]

Hi,

Is it appropriate to use CNAME to Alias a machine in a completely different domain such that it appears to be a machine in a domain "controlled" (if that's the right word) by our Primary DNS?

ie. I want fred.xxx.net to appear to be in our domain as fred.yyy.com - our DNS forwards to this host (the .net one) which is also a DNS in that domain (and will eventually be an Active Directory server to all our domains). It is accessible directly from our network.
An nslookup to our DNS presently shows it up as it really is.

We have used CNAMES extensively within many of the domains defined in our DNS system but it is usually (well, always as far as I can tell) just an aliasing of another name to the real one within the same domain or sub- domain.

ie. .yyy.com aliased to fred.yyy.com


thanks in advance for any assistance -I'm just treading carefully as we have a fairly complex DNS setup, and I really don't know that testing this in isolation is going to prove what might happen in the real world.

I read somewhere that DNS's should not be aliased???

regards

David

[Marc Roger]

CNAMEs are OK, provided they are the only RR, and they should not be used as targets of for NS and MX RR (RFC 2181 "Clarifications to the DNS Specification", 10.3):

10.3. MX and NS records

The domain name used as the value of a NS resource record, or part of the value of a MX resource record must not be an alias. Not only is the specification clear on this point, but using an alias in either of these positions neither works as well as might be hoped, nor well fulfills the ambition that may have led to this approach. This domain name must have as its value one or more address records. Currently those will be A records, however in the future other record types giving addressing information may be acceptable. It can also have other RRs, but never a CNAME RR.

[Thomas Bianco]

I cannot speak to the standard, but I can say that this functions perfectly in our environment.

A MUCH larger company purchased my company, and our ERP was moved to the HQ datacentre. All we did was alias* localerp.localsite.oldcompany.com to oldcomapnyerp.datacenter.hq.bigcorp.com

When we reintegrated our DNS hierarchy later on, we ended up aliasing everything in localsite.oldcompany.com to Bizgroup.bigcorp.com to ease migration woes. localsite.oldcompany.com still exists, but only as a container for CNAMEs in an un unmaintained state.


*This story is true; the names have been changed to protect the cowardly, er ah innocent.