One thing that CNAMES does allow is for grouping/seperation..
Say I have three large groups of domains for which I provide three
different types of service, lets call the services I provide foomail,
barmail, and bazmail. I currently provide all three services on the
same physicial server, which has its REAL hostname. but I want to
preserve the option of easily splitting them out to seperate servers
once the load increases. I illustrate with an example:
dom1.com in MX 10 barmail.mydomain.com.
dom2.com in MX 10 barmail.mydomain.com.
dom3.com in MX 10 barmail.mydomain.com.
dom4.com in MX 10 barmail.mydomain.com.
dom5.com in MX 10 barmail.mydomain.com.
dom1.net in MX 10 foomail.mydomain.com.
dom2.net in MX 10 foomail.mydomain.com.
dom3.net in MX 10 foomail.mydomain.com.
dom4.net in MX 10 foomail.mydomain.com.
dom5.net in MX 10 foomail.mydomain.com.
dom1.org in MX 10 bazmail.mydomain.com.
dom2.org in MX 10 bazmail.mydomain.com.
dom3.org in MX 10 bazmail.mydomain.com.
dom4.org in MX 10 bazmail.mydomain.com.
dom5.org in MX 10 bazmail.mydomain.com.
barmail.mydomain.com in CNAME realname.mydomain.com.
foomail.mydomain.com in CNAME realname.mydomain.com.
bazmail.mydomain.com in CNAME realname.mydomain.com.
Assuming 100+ domains in each group, its a LOT easier to just change
one CNAME, than to change the MX records for each and every one of the
domains. Also, say 'realname.mydomain.com' mail goes down, but its
still providing other services and I cant assign its name to something
else, so I want to move mail processing to 'otherserver.mydomain.com'..
Again, without using CNAMEs, I'm forced to edit hundreds of zone files.
CNAMES provide a way of doing this by mapping 'logical' or 'functional'
hostnames onto real hostnames. I dont think that was its original
purpose, but there isnt anything else that does..
On Tue, 11 Jan 2000, Philip Hazel wrote:
> On Tue, 11 Jan 2000, John Horne wrote:
>
> > We are running BIND 8.2.2. It does not complain about using CNAMES in the
> > data portion. Note that it is 'not recommended' according to the book
> > because of MTA's not using aliases - not that you cannot do it.
>
> It's unnecessary because MX records provide indirection for mail
> domains. So it's wasteful, which is reason enough to deprecate it.
>
> However, Exim does, I believe, work when it encounters this.
>
> --
> Philip Hazel University of Cambridge Computing Service,
> ph10@??? Cambridge, England. Phone: +44 1223 334714.
>
>
>
> --
> ## List details at http://www.exim.org/mailman/listinfo/exim-users Exim details at http://www.exim.org/ ##
>
