natecars at real-time.com writes: > mail A 10.0.0.1 > MX 5 mx1.example.com. > MX 5 mx2.example.com. > MX 10 offsitemx.example.com. > pop CNAME mail The only CNAME there is for pop, so it's legal. You aren't (I assume) trying to send mail to pop. (Why can't you say ALIAS instead of CNAME and have your DNS software automatically convert it to the correct A record?) > Or are you just saying that you can't have *different* MX records for > the CNAME than the record it's pointing to? That should be > self-obvious -- it's a pointer. You can't do this even if mail.example.net is an A record: example.com. CNAME example.net. example.com. 10 MX mail.example.net. This is specified in RFC 1034 section 3.6.2. > So if you don't use cnames at all, how do you do virtual hosting? IE: > > webserver.example.com. A 10.0.0.2 > www.customer1.example.com. CNAME webserver.example.com. > www.customer2.example.com. CNAME webserver.example.com. > www.customer3.example.com. CNAME webserver.example.com. In that case, you can use A records, since they are all hosted on the same DNS server. > This is especially important if, say, www.customer3.example.com is > hosted on the customer's own DNS server.. then if you need to change > webserver's ip address, it doesn't affect the customer, you just do > it. In that case, you could use a CNAME. But with the CNAME scheme, you will need another level of indirection: www.example.org. CNAME c3.customer.example.com. Otherwise, if you have customer3 and customer4 both pointing at webserver.example.com, you can't move them to separate servers without the customers updating their DNS records. But what about the bigger issue here? Most customers don't want their website to work on just www.example.org. They also want it to work on example.org. They also want to be able to receive mail for example.org. example.org cannot be a CNAME, since it can't co-exist with an MX record. > If the customer was adding an A record to your IP, you'd have to > make sure that they also update their DNS servers when the change is > made.. speaking from personal experience, customers have a tendancy > to ignore the three warnings in advance of the change and then they > get all pissed when their web site stops working. Yep. Which is why we don't support customers handling their own DNS. But we also provide mail and everything else, along with a web based DNS editor, so it's not an issue. -- David Phillips <david at acz.org> http://david.acz.org/ _______________________________________________ TCLUG Mailing List - Minneapolis/St. Paul, Minnesota http://www.mn-linux.org tclug-list at mn-linux.org https://mailman.real-time.com/mailman/listinfo/tclug-list